0NET REVENUES FROM COLLABORATIONS - Schedule of Revenue Recognized under Collaboration (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	$ 3,713,937	$ 2,248,243	$ 1,828,292
Regeneron Pharmaceuticals \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	113,957	302,798	100,468
Regeneron Pharmaceuticals \| Research Services Obligation \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	39,519	39,097	80,200
Regeneron Pharmaceuticals \| C5 License Obligation \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	21,635	38,341	(15,100)
Regeneron Pharmaceuticals \| C5 Monotherapy Obligation \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	0	191,520	0
Regeneron Pharmaceuticals \| C5 Co-Co Obligation \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	0	700	7,400
Regeneron Pharmaceuticals \| Regeneron Technology Transfer Obligation \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	2,431	0	0
Regeneron Pharmaceuticals \| Other license programs \| Global Strategic Collaboration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total net revenues from collaborations	$ 50,372	$ 33,140	$ 27,968