Product Revenues, Net - Schedule of Rollforward of Sales Allowances and Related Accruals (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Contract With Customer, Asset, Allowance For Credit Loss [Roll Forward]
Balance at beginning	$ 22,258	$ 25,659
Allowances for current period sales	135,575	55,492
Allowances for prior period sales	500	3,480
Payments and credits	(78,978)	(62,373)
Ending balance	79,355	22,258
Customer Credits, Fees and Discounts
Contract With Customer, Asset, Allowance For Credit Loss [Roll Forward]
Balance at beginning	7,577	15,482
Allowances for current period sales	23,746	14,410
Allowances for prior period sales	0	100
Payments and credits	(19,876)	(22,415)
Ending balance	11,447	7,577
Rebates, Chargebacks and Co-pay Assistance
Contract With Customer, Asset, Allowance For Credit Loss [Roll Forward]
Balance at beginning	14,681	10,177
Allowances for current period sales	111,829	41,082
Allowances for prior period sales	500	3,380
Payments and credits	(59,102)	(39,958)
Ending balance	$ 67,908	$ 14,681

INSMED Inc 10-K