XML 49 R31.htm IDEA: XBRL DOCUMENT v3.22.0.1

Leases (Tables)

12 Months Ended

Dec. 31, 2021

Leases [Abstract]

Schedule of components of lease expense

The components of lease expense were as follows:

			Years ended December 31,
			2021						2020						2019
Operating lease cost			$	3,502					$	2,755					$	2,160
Finance lease cost:
Amortization of right-of-use assets			$	169					$	101					$	75
Interest on lease liabilities			28						21						20
			$	197					$	122					$	95

Schedule of supplemental balance sheet information related to leases

Supplemental balance sheet information related to leases was as follows:

			Year ended December 31,
			2021						2020
Operating leases:
Operating lease right-of-use assets			$	12,889					$	10,936
Operating lease liabilities, current			$	2,303					$	1,437
Operating lease liabilities			$	11,247					$	10,158
Finance leases:
Property and equipment, gross			$	1,038					$	429
Property and equipment, accumulated depreciation			$	(345)					$	(176)
Other liabilities, current			$	239					$	93
Other liabilities			$	449					$	174
Weighted-average remaining lease term:
Operating leases			4.3 years						5.2 years
Finance leases			4.0 years						2.9 years
Weighted-average discount rate:
Operating leases			10.8		%				10.8		%
Finance leases			5.4		%				6.9		%

Schedule of supplemental cash flow information related to leases

Supplemental cash flow information related to leases was as follows:

			Year ended December 31,
			2021						2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases			$	3,241					$	2,394
Operating cash flows from finance leases			$	28					$	21
Financing cash flows from finance leases			$	215					$	116

Schedule of future minimum payments under operating leases

Future minimum lease payments under non-cancellable leases as of December 31, 2021 were as follows:

			Operating leases						Finance leases
2022			$	3,795					$	269
2023			3,909						262
2024			4,027						141
2025			4,147						48
2026 and thereafter			1,310						8
Total lease payments			17,188						728
Present value adjustment			(3,638)						(40)
Present value of lease liabilities			$	13,550					$	688

Schedule of future minimum payments on finance leases

Future minimum lease payments under non-cancellable leases as of December 31, 2021 were as follows:

			Operating leases						Finance leases
2022			$	3,795					$	269
2023			3,909						262
2024			4,027						141
2025			4,147						48
2026 and thereafter			1,310						8
Total lease payments			17,188						728
Present value adjustment			(3,638)						(40)
Present value of lease liabilities			$	13,550					$	688

X

- Definition

The tabular disclosure of supplemental balance sheet information related to leases.

+ References

No definition available.

+ Details

Name:	mrsn_LesseeOperatingAndFinanceLeaseSupplementalBalanceSheetInformationTableTextBlock
Namespace Prefix:	mrsn_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The tabular disclosure of supplemental cash flows information related to leases.

+ References

No definition available.

+ Details

Name:	mrsn_LesseeOperatingAndFinanceLeaseSupplementalCashFlowInformationTableTextBlock
Namespace Prefix:	mrsn_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Tabular disclosure of undiscounted cash flows of finance lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to finance lease liability recognized in statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918701-209980

+ Details

Name:	us-gaap_FinanceLeaseLiabilityMaturityTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Tabular disclosure of lessee's lease cost. Includes, but is not limited to, interest expense for finance lease, amortization of right-of-use asset for finance lease, operating lease cost, short-term lease cost, variable lease cost and sublease income.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980

+ Details

Name:	us-gaap_LeaseCostTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_LeasesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Tabular disclosure of undiscounted cash flows of lessee's operating lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to operating lease liability recognized in statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918701-209980

+ Details

Name:	us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration