Leases - Narrative (Details) $ in Thousands	1 Months Ended		12 Months Ended
	Jan. 31, 2022 USD ($) contract period	Jul. 31, 2017 period	Dec. 31, 2025 USD ($)	Sep. 30, 2025	Dec. 31, 2024 USD ($)	Apr. 30, 2018 USD ($)
Lessee Lease Description [Line Items]
Liabilities under lease			$ 59,982
Right-of-use assets			40,532		$ 57,536
Impairment loss on right-of-use asset			10,600
Watertown Lease
Lessee Lease Description [Line Items]
Liabilities under lease	$ 44,100
Right-of-use assets	$ 44,400
Watertown Lease | Office and Laboratory Space
Lessee Lease Description [Line Items]
Lease contract term		10 years
Number of extensions | period		1
Lease extension term		5 years				5 years
Liabilities under lease						$ 15,100
Right-of-use assets						16,700
Construction costs						$ 1,500
Watertown Lease | Newly Leased Space
Lessee Lease Description [Line Items]
Number of extensions | period	1
Lease extension term	5 years
Liabilities under lease	$ 20,100
Right-of-use assets	$ 20,100
Lease term	10 years
Tenant improvements	$ 2,600
Restricted cash			$ 3,300		$ 3,300
Number of amended lease separate contracts | contract	2
2025 Sublease
Lessee Lease Description [Line Items]
Lease extension term				2 years