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Employee Benefits - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average fair value of options granted		$ 12.62	$ 7.04
Share-based payment award, fair value assumptions, method used		Black Scholes option pricing model	Hull White
Number of options granted		1,048,317	881,671
Risk-free interest rate		1.50%	2.70%
Expected volatility		93.90%	87.90%
Weighted average expected term		6 years 1 month 6 days
Weighted-average contractual term			10 years
Postemployment Retirement Benefits
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Executive settlement, cash compensation to be paid				$ 0.9
Executive settlement, cash compensation paid	$ 0.9
Executive settlement expense				$ 1.8
Postemployment Retirement Benefits \| RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant of RSUs				30,000

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 165,800	$ 197,612
Marketable securities	48,234	42,153
Accounts receivable	244	941
Accounts receivable (related party)	1,258	1,711
Prepaid expenses and other current assets	9,915	4,951
Total current assets	225,451	247,368
Marketable securities		2,009
Property and equipment, net	3,545	3,715
Operating lease right-of-use assets	4,841	5,215
Intangible assets, net	2,739	2,876
Deferred tax assets	111	288
Other assets	1,275	1,905
Total assets	237,962	263,376
Current liabilities:
Accounts payable	3,381	3,029
Accrued expenses	12,159	13,536
Current portion of lease obligation	1,393	1,380
Current portion of deferred revenue	1,176	941
Current portion of deferred revenue (related party)	17,458	17,901
Total current liabilities	35,567	36,787
Lease obligation	3,484	3,872
Deferred revenue, net of current portion	270	780
Deferred revenue, net of current portion (related party)	84,055	90,637
Total liabilities	123,376	132,076
Stockholders’ equity:
Common shares	2,931	2,918
Additional paid-in capital	444,275	441,395
Accumulated other comprehensive (loss) income	(1,521)	1,586
Accumulated deficit	(331,099)	(314,599)
Total stockholders’ equity	114,586	131,300
Total liabilities and stockholders’ equity	$ 237,962	$ 263,376

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (16,500)	$ (7,083)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization of property and equipment	258	188
Amortization of intangible assets	66	57
Foreign exchange gain	(2,828)	(2,116)
Loss on disposal of property and equipment	16	0
Stock-based compensation expense	2,291	1,260
Amortization of discount on investments	(47)	(209)
Deferred tax expense	177	148
Changes in operating assets and liabilities:
Accounts receivable	1,092	(733)
Operating lease right-of-use assets and lease obligations	3	3
Prepaid expenses and other current assets	(4,656)	(284)
Accounts payable	386	1,099
Accrued expenses	(916)	(2,018)
Deferred revenue	(4,602)	(3,822)
Net cash used in operating activities	(25,260)	(13,510)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of marketable securities	(17,091)	(11,263)
Proceeds from maturities of marketable securities	13,251	19,717
Purchases of intangible assets	0	(178)
Purchases of property and equipment	(148)	(421)
Net cash (used in) provided by investing activities	(3,988)	7,855
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs	(164)	0
Proceeds from stock options exercised	602	28
Net cash provided by financing activities	438	28
Foreign exchange impact on cash, cash equivalents and restricted cash	(3,002)	(2,004)
Net decrease in cash, cash equivalents and restricted cash	(31,812)	(7,631)
Cash, cash equivalents, and restricted cash, beginning of period	197,813	164,730
Cash, cash equivalents, and restricted cash, end of period	166,001	157,099
SUPPLEMENTAL DISCLOSURES:
Non-cash purchases of property, equipment and intangibles	126	0
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents	165,800	156,959
Restricted cash included in non-current other assets	201	140
Cash, cash equivalents, and restricted cash, end of period	$ 166,001	$ 157,099

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The principal accounting policies applied in the preparation of these unaudited condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2019, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on March 16, 2020 (as amended, the “Annual Report on Form 10-K”). There have been no material changes in the Company’s significant accounting policies during the three months ended March 31, 2020.

Basis of Presentation

The Company prepared its unaudited consolidated condensed financial statements in compliance with generally accepted accounting principles in the U.S. ("U.S. GAAP"). Any reference in these notes to applicable guidance is meant to refer to authoritative U.S. GAAP as found in the Accounting Standards Codification ("ASC") and Accounting Standards Update ("ASU") of the Financial Accounting Standards Board ("FASB").

The unaudited condensed consolidated financial statements include the accounts of Merus N.V. and its wholly owned, controlled subsidiary, Merus US, Inc. All intercompany transactions and balances of subsidiaries have been eliminated in consolidation. In the opinion of management, these financial statements reflect furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the unaudited condensed consolidated financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended March 31, 2020 and 2019 are referred to as the first quarter of 2020 and 2019, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Certain prior period amounts have been reclassified to conform to the current period presentation.

The unaudited condensed consolidated financial statements presented herein do not contain the required disclosures under U.S. GAAP for annual financial statements. Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the annual audited consolidated financial statements and related notes as of and for the year ended December 31, 2019, included in the Annual Report on Form 10-K.

Going Concern

At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern.

The Company’s evaluation entails analyzing prospective operating budgets and forecasts for expectations of the Company’s cash needs, and comparing those needs to the current cash, cash equivalent and marketable securities balances. After considering the Company’s current research and development plans, the timing expectations related to the progress of its clinical-stage programs and its plans to pursue commercialization of any approved antibody candidate, and after considering its existing cash, cash equivalents and marketable securities as of March 31, 2020, the Company did not identify conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date these financial statements were issued.

Pending Accounting Pronouncements

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The new guidance aligns the requirements for capitalizing implementation costs incurred in a cloud-based hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). This ASU is effective for the Company at the beginning of 2021, including interim periods within that reporting period, although early adoption is permitted. The Company does not expect the impact of adoption to be significant.

In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808), which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and precludes recognizing as revenue consideration received from a collaborative arrangement participant if the participant is not a customer. The ASU will be effective for the Company in the first quarter of 2021, with early adoption permitted. As of March 31, 2020, none of the Company’s arrangements fall within the scope of ASC 808. However, as the Company may engage in future collaborative arrangements in the future, this ASU may apply to those new arrangements.

Employee Benefits

3 Months Ended

Mar. 31, 2020

Compensation And Retirement Disclosure [Abstract]

Employee Benefits

9. Employee Benefits

Share-Based Payments

Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:

	Three Months Ended March 31,
	2020		2019
	(In thousands)
Research and development	$	1,023	$	828
General and administrative		1,268		432
Total	$	2,291	$	1,260

The weighted-average grant date fair value of options, estimated as of the grant date using the Black Scholes option pricing model (2019: Hull White), was $12.62 per option (2019: $7.04 per option) for the 1,048,317 options (2019: 881,671 options) granted during the three months ended March 31, 2020, respectively. The significant weighted average valuation inputs included the risk-free interest rate 1.5% (2019: 2.7%), and volatility 93.9% (2019: 87.9%). A weighted average expected term of 6.1 years was used in the Black-Scholes option pricing model during the three months ended March 31, 2020 and the weighted-average contractual term of 10.0 years was used in the Hull White model during the three months ended March 31, 2019. The Company updates its valuation estimates and methodology to estimate the grant-date fair value of stock-based compensation periodically to reflect observable market data and exercise behavior.

Executive Settlement

In December 2019, in connection with the departure of the Chief Executive Officer of the Company, the Company awarded benefits, including the following: cash compensation of $0.9 million, a grant of 30,000 RSUs, extended vesting of his equity incentive awards through June 30, 2021 and extended exercisability of his equity incentive awards through December 31, 2021. The cash compensation was paid by the Company on January 31, 2020. There were no substantive service conditions associated with the benefits awarded other than the passage of time. The Company incrementally recognized $1.8 million in general and administrative expense associated with these benefits in the consolidated statement of operations for the year ended December 31, 2019.

Employee Benefits (Tables)

3 Months Ended

Mar. 31, 2020

Compensation And Retirement Disclosure [Abstract]

Summary of Share-based Compensation Expense Classified in Condensed Consolidated Statements of Operations and Comprehensive Loss

Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:

	Three Months Ended March 31,
	2020		2019
	(In thousands)
Research and development	$	1,023	$	828
General and administrative		1,268		432
Total	$	2,291	$	1,260

Collaborations (Tables)

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Summary of Company's Accompanying Condensed Consolidated Financial Statements Attributable to Transactions Arising From Collaboration Arrangements

The following tables provide amounts by year indicated and by line item included in the Company's accompanying condensed consolidated financial statements attributable to transactions arising from its collaboration arrangements. The dollar amounts in the tables below are in thousands.

	Related Party			Third Party
	Incyte			Ono			Other			Total
CONTRACT ASSETS
Accounts receivable
Balance at January 1, 2019	$	—		$	786		$	—		$	786
Billings		1,679			—			151			151
Cash receipts		(1,664	)		(772	)		—			(772	)
Foreign exchange		(15	)		(14	)		—			(14	)
Balance at March 31, 2020		—			—			151			151

Unbilled receivables
Balance at January 1, 2019	$	1,711		$	—		$	155		$	155
Accrued receivables		1,266			—			94			94
Billings		(1,679	)		—			(151	)		(151	)
Foreign exchange		(40	)		—			(5	)		(5	)
Balance at March 31, 2020		1,258			—			93			93

CONTRACT LIABILITIES
Deferred revenue
Balance at January 1, 2019	$	108,538		$	336		$	1,385		$	1,721
Revenue recognized in the period		(4,368	)		(49	)		(185	)		(234	)
Foreign exchange		(2,657	)		(8	)		(33	)		(41	)
Balance at March 31, 2020		101,513			279			1,167			1,446
Less: current portion		(17,458	)		(192	)		(984	)		(1,176	)
Non-current balance at March 31, 2020		84,055			87			183			270

Summary of Company's Collaboration Arrangements Earned in Period to Be Billed and Collected in Next Period

The balance of unbilled receivables predominantly represents reimbursement revenue under the Company’s collaboration arrangements earned in the period to be billed and collected in the next period, generally quarterly. Incyte is a related party as a shareholder, as more fully described in Note 10.

Contract Revenues and Expenses

	Three Months Ended March 31, 2020
	(In thousands)
	Related Party		Third Party
	Incyte		Ono		Other		Total
Upfront payments	$	4,368	$	49	$	150	$	199
Reimbursement revenue		1,605		—		94		94
Milestones		—		—		35		35
Total collaboration revenue	$	5,973	$	49	$	279	$	328
Operating expenses:
Research and development expense	$	340	$	—	$	—	$	—
General and administrative expense		—		—		—		—
Total operating expenses from collaborations	$	340	$	—	$	—	$	—
Revenue recognized that was included in deferred revenue at the beginning of the period	$	4,368	$	49	$	185	$	234

	Three Months Ended March 31, 2019
	(In thousands)
	Related Party		Third Party
	Incyte		Ono		Other		Total
Upfront payments	$	4,463	$	50	$	188	$	238
Reimbursement revenue		2,764		99		45		144
Milestones		—		1,136		84		1,220
Total collaboration revenue	$	7,227	$	1,285	$	317	$	1,602
Operating expenses:
Research and development expense	$	137	$	—	$	—	$	—
General and administrative expense		—		—		—		—
Total operating expenses from collaborations	$	137	$	—	$	—	$	—
Revenue recognized that was included in deferred revenue at the beginning of the period	$	4,463	$	50	$	272	$	322

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Preparation	Basis of Presentation The Company prepared its unaudited consolidated condensed financial statements in compliance with generally accepted accounting principles in the U.S. ("U.S. GAAP"). Any reference in these notes to applicable guidance is meant to refer to authoritative U.S. GAAP as found in the Accounting Standards Codification ("ASC") and Accounting Standards Update ("ASU") of the Financial Accounting Standards Board ("FASB"). The unaudited condensed consolidated financial statements include the accounts of Merus N.V. and its wholly owned, controlled subsidiary, Merus US, Inc. All intercompany transactions and balances of subsidiaries have been eliminated in consolidation. In the opinion of management, these financial statements reflect furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the unaudited condensed consolidated financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The three months ended March 31, 2020 and 2019 are referred to as the first quarter of 2020 and 2019, respectively. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Certain prior period amounts have been reclassified to conform to the current period presentation. The unaudited condensed consolidated financial statements presented herein do not contain the required disclosures under U.S. GAAP for annual financial statements. Therefore, these unaudited condensed consolidated financial statements should be read in conjunction with the annual audited consolidated financial statements and related notes as of and for the year ended December 31, 2019, included in the Annual Report on Form 10-K.
Going Concern	Going Concern At each reporting period, the Company evaluates whether there are conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the financial statements are issued. The Company is required to make certain additional disclosures if it concludes substantial doubt exists and it is not alleviated by the Company’s plans or when its plans alleviate substantial doubt about the Company’s ability to continue as a going concern. The Company’s evaluation entails analyzing prospective operating budgets and forecasts for expectations of the Company’s cash needs, and comparing those needs to the current cash, cash equivalent and marketable securities balances. After considering the Company’s current research and development plans, the timing expectations related to the progress of its clinical-stage programs and its plans to pursue commercialization of any approved antibody candidate, and after considering its existing cash, cash equivalents and marketable securities as of March 31, 2020, the Company did not identify conditions or events that raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date these financial statements were issued.
Pending Accounting Pronouncements	Pending Accounting Pronouncements In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The new guidance aligns the requirements for capitalizing implementation costs incurred in a cloud-based hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). This ASU is effective for the Company at the beginning of 2021, including interim periods within that reporting period, although early adoption is permitted. The Company does not expect the impact of adoption to be significant. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808), which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and precludes recognizing as revenue consideration received from a collaborative arrangement participant if the participant is not a customer. The ASU will be effective for the Company in the first quarter of 2021, with early adoption permitted. As of March 31, 2020, none of the Company’s arrangements fall within the scope of ASC 808. However, as the Company may engage in future collaborative arrangements in the future, this ASU may apply to those new arrangements.

Leases

3 Months Ended

Mar. 31, 2020

Leases [Abstract]

Leases

7. Leases

There have been no changes in the Company’s lease arrangements since December 31, 2019.

	Three Months Ended March 31,
	2020		2019
	(In thousands)
Lease cost
Operating lease cost	$	396	$	243
Variable lease cost		82		51
Total lease cost included in operating expenses	$	478	$	294
Other information
Cash paid for amounts included in the measurement of lease liabilities included in operating cash flows	$	393		240

Income Taxes (Tables)

3 Months Ended

Mar. 31, 2020

Income Tax Disclosure [Abstract]

Summary of Components of Expense for (Benefit) from Income Taxes

The components of the income tax expense (benefit) from continuing operations are as follows:

	Three Months Ended March 31,
	2020			2019
	(In thousands)
U.S. federal	$	(56	)	$	54
U.S. state		(24	)		20
Total current tax (benefit) expense	$	(80	)	$	74

U.S. federal	$	125		$	105
U.S. state		52			43
Total deferred tax expense	$	177		$	148

Total tax expense	$	97		$	222

Collaborations

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaborations

8. Collaborations

Incyte

On January 23, 2017, the Company completed the sale of shares and exchange of a license. The Company initially deferred $152.6 million of the transaction price allocated to the license and related activities performance obligation as deferred revenue, to be recognized as revenue over time as the primary benefit of the license to Incyte is access to the platform for the generation of potential product candidates. Development milestones, commercialization milestones and royalties are variable consideration, fully constrained, to be recognized in future periods in accordance with the Company’s revenue recognition policy. Cost reimbursements for research services are recognized as they are performed over time as these are considered a separate performance obligation.

At March 31, 2020, the Company is currently engaged in research and development activities for MCLA-145 and developing candidates for the other programs. No development or commercialization milestones have been achieved to date.

ONO

On March 14, 2018, the Company granted ONO an exclusive, worldwide, royalty-bearing license, with the right to sublicense, research, test, make, use and market a limited number of bispecific antibody candidates based on the Company’s Biclonics^® technology platform against two undisclosed targets directed to a particular undisclosed target combination. ONO agreed to pay the Company an upfront, non-refundable payment of €0.7 million. In addition, the Company was entitled to €0.3 million intended to compensate the Company for research services already completed upon entering into the agreement, and €0.2 million to be paid to the Company over time for full time equivalent funding. The Company is entitled to research and development milestones in addition to royalties on future sales. The Company identified performance obligations for: (1) provision of a license for the target combination, and (2) research and development services. The Company concluded that Ono would be able to develop and benefit from the license, independent of the research and development services. The research and development services are capable of being performed by third parties with an appropriate sub-license, and are recognized over time as these services are delivered. Milestone payments are fully constrained as variable consideration to be recognized in future periods in accordance with the Company’s revenue recognition policy.

Amounts related to the provision of a license are amortized over the intended period of use. The Company received €1.0 million (approximately $1.1 million) for the quarter ended March 31, 2019 for development milestones received from Ono based on their progress.

Simcere

In January 2018, the Company granted Simcere an exclusive license to develop and commercialize three bispecific antibodies to be produced by Merus utilizing the Company’s Biclonics^® technology platform in the area of immuno-oncology in China. The Company received an upfront, non-refundable payment of $2.75 million, relating to three separate research programs. The Company may be entitled to future development milestone payments. The Company will be eligible to receive tiered royalty payments on sales of any products resulting from the collaboration in China from Simcere. Simcere will be eligible to receive tiered royalty payments on sales outside of China from the Company.

At inception of the arrangement, the Company identified three performance obligations comprised of the combined delivery of a license and performance of research and development activities with respect to each program. The Company performs research and development activities to achieve candidate nomination. The Company concluded that these activities were not distinct from the underlying license for each program as Simcere would not be able to benefit from the license apart from research and development activities at this phase of development.

The transaction price under the arrangement comprised fixed consideration of $2.75 million. The transaction price was allocated to each separate performance obligation on a relative standalone fair value basis. The Company deferred the portion of the upfront payment allocated to the three performance obligations as deferred revenue, to be recognized over time. Compensation for research and development services prior to candidate nomination are allocated to each program performance obligation and also recognized over time. Development milestone payments allocated to each of the program performance obligations are constrained as variable consideration to be recognized in future periods in accordance with the Company’s revenue recognition policy.

To date, the Company has achieved one milestone under this agreement and has received an aggregate of $0.8 million in milestone payments. At March 31, 2020, research and development for three of the three programs is on-going, with the first two programs under going active research and discovery efforts and the third completing the planning phase, with active research planned in the near term.

Contract Assets and Liabilities

	Related Party			Third Party
	Incyte			Ono			Other			Total
CONTRACT ASSETS
Accounts receivable
Balance at January 1, 2019	$	—		$	786		$	—		$	786
Billings		1,679			—			151			151
Cash receipts		(1,664	)		(772	)		—			(772	)
Foreign exchange		(15	)		(14	)		—			(14	)
Balance at March 31, 2020		—			—			151			151

Unbilled receivables
Balance at January 1, 2019	$	1,711		$	—		$	155		$	155
Accrued receivables		1,266			—			94			94
Billings		(1,679	)		—			(151	)		(151	)
Foreign exchange		(40	)		—			(5	)		(5	)
Balance at March 31, 2020		1,258			—			93			93

CONTRACT LIABILITIES
Deferred revenue
Balance at January 1, 2019	$	108,538		$	336		$	1,385		$	1,721
Revenue recognized in the period		(4,368	)		(49	)		(185	)		(234	)
Foreign exchange		(2,657	)		(8	)		(33	)		(41	)
Balance at March 31, 2020		101,513			279			1,167			1,446
Less: current portion		(17,458	)		(192	)		(984	)		(1,176	)
Non-current balance at March 31, 2020		84,055			87			183			270

Contract Revenues and Expenses

	Three Months Ended March 31, 2020
	(In thousands)
	Related Party		Third Party
	Incyte		Ono		Other		Total
Upfront payments	$	4,368	$	49	$	150	$	199
Reimbursement revenue		1,605		—		94		94
Milestones		—		—		35		35
Total collaboration revenue	$	5,973	$	49	$	279	$	328
Operating expenses:
Research and development expense	$	340	$	—	$	—	$	—
General and administrative expense		—		—		—		—
Total operating expenses from collaborations	$	340	$	—	$	—	$	—
Revenue recognized that was included in deferred revenue at the beginning of the period	$	4,368	$	49	$	185	$	234

	Three Months Ended March 31, 2019
	(In thousands)
	Related Party		Third Party
	Incyte		Ono		Other		Total
Upfront payments	$	4,463	$	50	$	188	$	238
Reimbursement revenue		2,764		99		45		144
Milestones		—		1,136		84		1,220
Total collaboration revenue	$	7,227	$	1,285	$	317	$	1,602
Operating expenses:
Research and development expense	$	137	$	—	$	—	$	—
General and administrative expense		—		—		—		—
Total operating expenses from collaborations	$	137	$	—	$	—	$	—
Revenue recognized that was included in deferred revenue at the beginning of the period	$	4,463	$	50	$	272	$	322

Employee Benefits - Summary of Share-based Compensation Expense Classified in Condensed Consolidated Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total	$ 2,291	$ 1,260
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total	1,023	828
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total	$ 1,268	$ 432

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Registrant Name	Merus N.V.
Trading Symbol	MRUS
Entity Central Index Key	0001651311
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding		29,035,900
Entity File Number	001-37773
Entity Incorporation, State or Country Code	P7
Entity Tax Identification Number	00-0000000
Entity Address, Address Line One	Yalelaan 62
Entity Address, City or Town	Utrecht
Entity Address, Postal Zip Code	3584 CM
Entity Address, Country	NL
City Area Code	+31 85
Local Phone Number	016 2500
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common shares, nominal value €0.09 per share
Security Exchange Name	NASDAQ

Collaborations - Additional Information (Details) $ in Thousands, € in Millions				1 Months Ended	3 Months Ended
	Aug. 31, 2018 USD ($)	Mar. 14, 2018 EUR (€)	Jan. 23, 2017 USD ($)	Jan. 31, 2018 USD ($) Antibody PerformanceObligation Milestone	Mar. 31, 2020 USD ($)	Mar. 31, 2020 EUR (€)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestones received					$ 1,100	€ 1.0
Incyte Collaboration and License Agreement \| License and Related Activities
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborations, transaction price as deferred revenue			$ 152,600
Second ONO Research and License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable upfront payment receivable \| €		€ 0.7
Payment to compensate research services \| €		0.3
Over time payment for full time equivalent funding \| €		€ 0.2
Simcere Collaboration and License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of bispecific antibodies under collaboration and license agreement \| Antibody				3
Non-refundable upfront payment received				$ 2,750
Collaborations, transaction price as revenue				$ 2,750
Milestone payments received	$ 800
Number of milestones achieved \| Milestone				1
Description of transaction price under fixed consideration					research and development for three of the three programs is on-going, with the first two programs under going active research and discovery efforts and the third completing the planning phase, with active research planned in the near term	research and development for three of the three programs is on-going, with the first two programs under going active research and discovery efforts and the third completing the planning phase, with active research planned in the near term
Simcere Collaboration and License Agreement \| License and Performance \| Research and Development
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligation \| PerformanceObligation				3

Supplemental Balance Sheet Information (Tables)

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following:

	March 31, 2020		December 31, 2019
	(In thousands)
Prepaid clinical and manufacturing costs	$	4,443	$	2,779
Prepaid general and administrative expenses		3,378		789
Interest receivable		215		259
Other		1,879		1,124
Total	$	9,915	$	4,951

Summary of Accrued Expenses

Accrued expenses consisted of the following:

	March 31, 2020		December 31, 2019
	(In thousands)
Accrued research and development expenses	$	8,805	$	6,618
Accrued general and administrative expenses		1,567		2,402
Accrued personnel costs		1,751		4,495
Other		36		21
Total	$	12,159	$	13,536

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - € / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common shares, par value	€ 0.09	€ 0.09
Common shares, authorized	45,000,000	45,000,000
Common shares, issued	29,009,422	28,882,217
Common shares, outstanding	29,009,422	28,882,217

Overview

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Overview

1. Overview

Merus N.V. is a clinical-stage immuno-oncology company developing innovative antibody therapeutics, headquartered in Utrecht, the Netherlands. Merus US, Inc. is a wholly-owned subsidiary of Merus N.V. located at 139 Main Street, Cambridge, Massachusetts, United States (collectively, the “Company”).

Since inception, the Company has generated an accumulated deficit of $331.1 million as of March 31, 2020. The Company expects to continue to incur significant expenses and operating losses for the foreseeable future as its antibody candidates advance through discovery, pre-clinical development and clinical trials and as it seeks regulatory approval and pursues commercialization of any approved antibody candidate.

As a result, the Company may need additional financing to support its continuing operations. Until the Company can generate significant revenue from product sales, if ever, the Company expects to finance its operations through public equity offerings, debt financings, or other sources, which may include collaborations with third parties and business development opportunities. Adequate additional financing may not be available to the Company on acceptable terms, or at all. The Company’s inability to raise capital as and when needed would have a negative impact on its financial condition and ability to pursue its business strategy. The Company will need to generate significant revenues to achieve profitability and may never do so.

Based on the Company’s current operating plan, the Company expects that its existing cash and cash equivalents and marketable securities of $214.0 million as of March 31, 2020 will be sufficient to fund its operations into 2022.

Overview - Additional Information (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (331,099)	$ (314,599)
Cash and cash equivalents and marketable securities	$ 214,000

Collaborations - Summary of Company's Collaboration Arrangements Earned in Period to Be Billed and Collected in Next Period (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating expenses:
Research and development	$ 16,987	$ 11,799
General and administrative	8,882	6,741
Total operating expenses	25,869	18,540
Incyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payments	4,368	4,463
Reimbursement revenue	1,605	2,764
Milestones	0	0
Total collaboration revenue	5,973	7,227
Operating expenses:
Research and development	340	137
General and administrative	0	0
Total operating expenses	340	137
Revenue recognized in the period	4,368	4,463
Ono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payments	49	50
Reimbursement revenue	0	99
Milestones	0	1,136
Total collaboration revenue	49	1,285
Operating expenses:
Research and development	0	0
General and administrative	0	0
Total operating expenses	0	0
Revenue recognized in the period	49	50
Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payments	150	188
Reimbursement revenue	94	45
Milestones	35	84
Total collaboration revenue	279	317
Operating expenses:
Research and development	0	0
General and administrative	0	0
Total operating expenses	0	0
Revenue recognized in the period	185	272
Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payments	199	238
Reimbursement revenue	94	144
Milestones	35	1,220
Total collaboration revenue	328	1,602
Operating expenses:
Research and development	0	0
General and administrative	0	0
Total operating expenses	0	0
Revenue recognized in the period	$ 234	$ 322

Subsequent Events

3 Months Ended

Mar. 31, 2020

Subsequent Events [Abstract]

Subsequent Events

11. Subsequent Events

On April 15, 2020, Mark Throsby, Ph.D. resigned as the Executive Vice President and Chief Scientific Officer of the Company effective July 31, 2020. In connection with his departure, Mr. Throsby has entered into a Settlement Agreement with the Company, pursuant to which Mr. Throsby will be entitled to receive a severance payment equal to 8 months of his annual salary and amortized bonus aggregating approximately $0.3 million. Further, subject to Mr. Throsby’s continued compliance with the terms and conditions of the Settlement Agreement, Mr. Throsby’s unvested equity awards granted to him under the applicable equity-based long-term incentive plan of the Company will continue to vest until October 31, 2020 as if Mr. Throsby had continued in full time service with the Company through such date. The Company is evaluating the accounting for the modification of his unvested equity awards.

Investments in Debt Securities - Summary of Investments in Debt Securities in Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	$ 71,483	$ 78,215
Fair value of debt securities	71,465	78,254
Cash equivalents [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	23,249	34,053
Current marketable securities [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	48,234	42,153
Non-current marketable securities [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	0	2,009
Money market funds [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	23,249	34,053
Corporate paper and notes [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	44,240	38,679
U.S. government agency securities [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	2,495	3,987
U.S. treasuries [member]
Debt Securities Held To Maturity Nonaccrual [Line Items]
Total	$ 1,499	$ 1,496

Related Party Transactions

3 Months Ended

Mar. 31, 2020

Related Party Transactions

10. Related Party Transactions

The Company has entered into the Incyte collaboration and license agreement and the Incyte share subscription agreement with amounts related to transactions under the arrangement disclosed in Note 8 and the arrangement described in the Company’s annual consolidated financial statements for the year ended December 31, 2019. Incyte is a shareholder with holdings representing approximately 11.0% of the outstanding shares of the Company as of March 31, 2020, and 11.1% as of December 31, 2019.

Leases (Tables)

3 Months Ended

Mar. 31, 2020

Leases [Abstract]

Summary of Components of Lease Cost

	Three Months Ended March 31,
	2020		2019
	(In thousands)
Lease cost
Operating lease cost	$	396	$	243
Variable lease cost		82		51
Total lease cost included in operating expenses	$	478	$	294
Other information
Cash paid for amounts included in the measurement of lease liabilities included in operating cash flows	$	393		240

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Total revenue	$ 6,301	$ 8,829
Operating expenses:
Research and development	16,987	11,799
General and administrative	8,882	6,741
Total operating expenses	25,869	18,540
Operating loss	(19,568)	(9,711)
Other income, net:
Interest income, net	280	630
Foreign exchange gains	2,885	2,220
Other income, net	3,165	2,850
Net loss before income taxes	(16,403)	(6,861)
Tax expense	97	222
Net loss	(16,500)	(7,083)
Other comprehensive loss:
Currency translation adjustment	(3,107)	(1,900)
Comprehensive loss	$ (19,607)	$ (8,983)
Net loss per share attributable to common stockholders: Basic and diluted	$ (0.68)	$ (0.38)
Weighted-average common shares outstanding: Basic and diluted	28,946	23,373
Collaboration Revenue [Member]
Total revenue from contracts with customers	$ 328	$ 1,602
Collaboration Revenue (Related Party) [Member]
Total revenue from contracts with customers	$ 5,973	$ 7,227

Investments in Debt Securities (Tables)

3 Months Ended

Mar. 31, 2020

Debt Securities [Abstract]

Summary of Investments in Debt Securities in Condensed Consolidated Balance Sheet

The following tables summarize the Company’s investments in debt securities and their presentation in the condensed consolidated balance sheet:

	March 31, 2020		December 31, 2019
	(in thousands)
Money market funds	$	23,249	$	34,053
Corporate paper and notes		44,240		38,679
U.S. government agency securities		2,495		3,987
U.S. treasuries		1,499		1,496
Total	$	71,483	$	78,215

Fair value of debt securities	$	71,465	$	78,254

	March 31, 2020		December 31, 2019
	(in thousands)
Cash equivalents	$	23,249	$	34,053
Current marketable securities		48,234		42,153
Non-current marketable securities		—		2,009
Total	$	71,483	$	78,215

Supplemental Balance Sheet Information - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued research and development expenses	$ 8,805	$ 6,618
Accrued general and administrative expenses	1,567	2,402
Accrued personnel costs	1,751	4,495
Other	36	21
Total	$ 12,159	$ 13,536

Investments in Debt Securities

3 Months Ended

Mar. 31, 2020

Debt Securities [Abstract]

Investments in Debt Securities

3. Investments in Debt Securities

The following tables summarize the Company’s investments in debt securities and their presentation in the condensed consolidated balance sheet:

	March 31, 2020		December 31, 2019
	(in thousands)
Money market funds	$	23,249	$	34,053
Corporate paper and notes		44,240		38,679
U.S. government agency securities		2,495		3,987
U.S. treasuries		1,499		1,496
Total	$	71,483	$	78,215

Fair value of debt securities	$	71,465	$	78,254

	March 31, 2020		December 31, 2019
	(in thousands)
Cash equivalents	$	23,249	$	34,053
Current marketable securities		48,234		42,153
Non-current marketable securities		—		2,009
Total	$	71,483	$	78,215

The Company does not intend to sell and it is unlikely that the Company will be required to sell the above investments before recovery of their amortized cost bases, which may be maturity. The Company determined that there was no material change in the credit risk of any of its investments.

The fair value of money market funds is determined based on publicly available market price for these funds (Level 1). The fair value of other debt securities is determined based on the publicly available inputs which includes a market price for the same or similar instruments adjusted for estimates in interest yield (Level 2).

Income Taxes

3 Months Ended

Mar. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

5. Income Taxes

The Company files income tax returns in the U.S. federal and Massachusetts jurisdictions as well as in the Netherlands. The components of the income tax expense (benefit) from continuing operations are as follows:

	Three Months Ended March 31,
	2020			2019
	(In thousands)
U.S. federal	$	(56	)	$	54
U.S. state		(24	)		20
Total current tax (benefit) expense	$	(80	)	$	74

U.S. federal	$	125		$	105
U.S. state		52			43
Total deferred tax expense	$	177		$	148

Total tax expense	$	97		$	222

After consideration of all positive and negative evidence, we believe that it is more-likely-than-not that the Netherlands deferred tax assets will not be realized that are not supported by reversing temporary differences. As a result, we established a full valuation allowance against deferred tax assets of the Netherlands.

Income Taxes - Summary of Components of Expense for (Benefit) from Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
U.S. federal	$ (56)	$ 54
U.S. state	(24)	20
Total current tax (benefit) expense	(80)	74
U.S. federal	125	105
U.S. state	52	43
Total deferred tax expense	177	148
Total tax expense	$ 97	$ 222

Supplemental Balance Sheet Information - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Prepaid Expense And Other Assets Current [Abstract]
Prepaid clinical and manufacturing costs	$ 4,443	$ 2,779
Prepaid general and administrative expenses	3,378	789
Interest receivable	215	259
Other	1,879	1,124
Total	$ 9,915	$ 4,951

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2018	$ 105,857	$ 2,366	$ 360,045	$ (259,448)	$ 2,894
Beginning balance, shares at Dec. 31, 2018		23,358,977
Exercise of stock options and vesting of restricted stock units	28	$ 2	26	0	0
Exercise of stock options and vesting of restricted stock units, shares		20,678
Stock-based compensation	1,260	$ 0	1,260	0	0
Currency translation adjustment	(1,900)	0	0	0	(1,900)
Net loss	(7,083)	0	0	(7,083)	0
Ending balance at Mar. 31, 2019	98,162	$ 2,368	361,331	(266,531)	994
Ending balance, shares at Mar. 31, 2019		23,379,655
Beginning balance at Dec. 31, 2019	131,300	$ 2,918	441,395	(314,599)	1,586
Beginning balance, shares at Dec. 31, 2019		28,882,217
Exercise of stock options and vesting of restricted stock units	602	$ 13	589	0	0
Exercise of stock options and vesting of restricted stock units, shares		127,205
Stock-based compensation	2,291	$ 0	2,291	0	0
Currency translation adjustment	(3,107)	0	0	0	(3,107)
Net loss	(16,500)	0	0	(16,500)	0
Ending balance at Mar. 31, 2020	$ 114,586	$ 2,931	$ 444,275	$ (331,099)	$ (1,521)
Ending balance, shares at Mar. 31, 2020		29,009,422

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Collaborations - Summary of Company's Accompanying Condensed Consolidated Financial Statements Attributable to Transactions Arising From Collaboration Arrangements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Incyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized in the period	$ 4,368	$ 4,463
Ono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized in the period	49	50
Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized in the period	185	272
Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized in the period	234	$ 322
Accounts Receivable \| Incyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	0
Billings	1,679
Cash receipts	(1,664)
Foreign exchange	(15)
Balance at March 31, 2020	0
Accounts Receivable \| Ono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	786
Billings	0
Cash receipts	(772)
Foreign exchange	(14)
Balance at March 31, 2020	0
Accounts Receivable \| Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	0
Billings	151
Cash receipts	0
Foreign exchange	0
Balance at March 31, 2020	151
Accounts Receivable \| Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	786
Billings	151
Cash receipts	(772)
Foreign exchange	(14)
Balance at March 31, 2020	151
Unbilled Receivables \| Incyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	1,711
Accrued receivables	1,266
Billings	(1,679)
Foreign exchange	(40)
Balance at March 31, 2020	1,258
Unbilled Receivables \| Ono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	0
Accrued receivables	0
Billings	0
Foreign exchange	0
Balance at March 31, 2020	0
Unbilled Receivables \| Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	155
Accrued receivables	94
Billings	(151)
Foreign exchange	(5)
Balance at March 31, 2020	93
Unbilled Receivables \| Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at January 1, 2019	155
Accrued receivables	94
Billings	(151)
Foreign exchange	(5)
Balance at March 31, 2020	93
Deferred Revenue \| Incyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Foreign exchange	(2,657)
Balance at January 1, 2019	108,538
Revenue recognized in the period	(4,368)
Balance at March 31, 2020	101,513
Less: current portion	(17,458)
Non-current balance at March 31, 2020	84,055
Deferred Revenue \| Ono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Foreign exchange	(8)
Balance at January 1, 2019	336
Revenue recognized in the period	(49)
Balance at March 31, 2020	279
Less: current portion	(192)
Non-current balance at March 31, 2020	87
Deferred Revenue \| Other
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Foreign exchange	(33)
Balance at January 1, 2019	1,385
Revenue recognized in the period	(185)
Balance at March 31, 2020	1,167
Less: current portion	(984)
Non-current balance at March 31, 2020	183
Deferred Revenue \| Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Foreign exchange	(41)
Balance at January 1, 2019	1,721
Revenue recognized in the period	(234)
Balance at March 31, 2020	1,446
Less: current portion	(1,176)
Non-current balance at March 31, 2020	$ 270

Related Party Transactions - Additional Information (Details)	Mar. 31, 2020	Dec. 31, 2019
Incyte \| Merus N V [Member]
Related Party Transaction [Line Items]
Ownership percentage	11.00%	11.10%

Supplemental Balance Sheet Information

3 Months Ended

Mar. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Supplemental Balance Sheet Information

4. Supplemental Balance Sheet Information

Prepaid expenses and other current assets consisted of the following:

	March 31, 2020		December 31, 2019
	(In thousands)
Prepaid clinical and manufacturing costs	$	4,443	$	2,779
Prepaid general and administrative expenses		3,378		789
Interest receivable		215		259
Other		1,879		1,124
Total	$	9,915	$	4,951

Accrued expenses consisted of the following:

	March 31, 2020		December 31, 2019
	(In thousands)
Accrued research and development expenses	$	8,805	$	6,618
Accrued general and administrative expenses		1,567		2,402
Accrued personnel costs		1,751		4,495
Other		36		21
Total	$	12,159	$	13,536

Subsequent Events - Additional Information (Details) - Postemployment Retirement Benefits - USD ($) $ in Millions	Apr. 15, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Executive settlement, cash compensation to be paid		$ 0.9
Subsequent Event
Subsequent Event [Line Items]
Executive settlement, cash compensation to be paid	$ 0.3

Operating Leases - Summary of Components of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Lease cost
Operating lease cost	$ 396	$ 243
Variable lease cost	82	51
Total lease cost included in operating expenses	478	294
Other information
Cash paid for amounts included in the measurement of lease liabilities included in operating cash flows	$ 393	$ 240

Commitments and Contingencies

3 Months Ended

Mar. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Litigation

On April 5, 2018, an unnamed third party and Regeneron Pharmaceuticals Inc. or Regeneron filed notices of opposition against the Company’s EP 2604625 patent, entitled “Generation of Binding Molecules,” in the European Opposition Division of the European Patent Office (the “EPO”). The notices asserted, as applicable, added subject matter, lack of novelty, lack of inventive step, and insufficiency. Regeneron withdrew its opposition pursuant to a global December 20, 2018 settlement with the Company. On August 20, 2018, the Company timely responded to these submissions with respect to the unnamed third party. An opposition hearing was held in June 2019, wherein the EPO revoked the EP 2604625 patent in its entirety under Art. 123(2) EPC. We timely appealed that decision in December 2019 before the Technical Board of Appeals for the EPO seeking reinstatement of the patent and proposing auxiliary requests for certain amended claims, with further proceedings to be scheduled in the future. As this opposition proceeding continues, the Company cannot be certain that the Company will ultimately prevail.

From time to time, the Company may be involved in various other claims and legal proceedings relating to claims arising out of the Company’s operations. The Company is not currently a party to any other material legal proceedings.