Collaboration Agreements (Tables)

6 Months Ended

Jun. 30, 2023

Collaboration Agreement [Abstract]

Summary of Operating Expenses Category Related to Collaboration Agreement

The following table summarizes expenses related to the Biogen Collaboration Agreement that were incurred by the Company and the related reimbursement from Biogen or to Biogen, reflected by category of operating expenses:

	Three Months Ended June 30,						Six Months Ended June 30,
	2023			2022			2023			2022
	(in thousands)
Expenses related to the Biogen Collaboration Agreement    incurred by Sage	$	71,524		$	59,218		$	127,660		$	107,972
Net reimbursement to (from) Biogen reflected in the    condensed consolidated statements of operations and    comprehensive loss:
Research and development expenses		(22,418	)		(20,983	)		(39,700	)		(39,497	)
Selling, general and administrative expenses		7,476			(2,835	)		10,510			(4,309	)
		(14,942	)		(23,818	)		(29,190	)		(43,806	)
Total net expenses related to the Biogen Collaboration    Agreement in the condensed consolidated statements of    operations and comprehensive loss	$	56,582		$	35,400		$	98,470		$	64,166