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Share-Based Payments - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jul. 31, 2025	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Share-based payments
Share-based compensation expense		$ 30,745	$ 7,674	$ 46,320	$ 20,123
Unrecognized compensation expense		14,400		14,400
Sage Therapeutics, Inc.
Share-based payments
Share-based compensation expense	$ 22,900
Research and development
Share-based payments
Share-based compensation expense		1,446	1,350	4,337	3,946
Selling, general and administrative
Share-based payments
Share-based compensation expense		$ 29,299	$ 6,324	$ 41,983	$ 16,177