XML 67 R57.htm IDEA: XBRL DOCUMENT v3.24.3

Restructuring - Narrative (Details)	Jul. 26, 2023
Restructuring and Related Activities [Abstract]
Percentage of positions to be eliminated	0.50

X

- Definition

The number of positions to be eliminated in connection with a restructuring plan, as a percentage of total current positions.

+ References

No definition available.

+ Details

Name:	mrsn_RestructuringAndRelatedCostNumberOfPositionsToBeEliminatedPercent
Namespace Prefix:	mrsn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

X

- References

No definition available.

+ Details

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