Revenues - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,208.3	$ 1,045.7	$ 2,277.2	$ 1,943.5
U.S.
Disaggregation of Revenue [Line Items]
Total revenues	1,077.9	936.3	2,037.7	1,734.8
Europe
Disaggregation of Revenue [Line Items]
Total revenues	97.4	82.7	189.8	165.7
All other
Disaggregation of Revenue [Line Items]
Total revenues	33.0	26.7	49.7	43.0
Product sales, net
Disaggregation of Revenue [Line Items]
Total revenues	1,156.1	985.6	2,181.4	1,825.0
Sleep
Disaggregation of Revenue [Line Items]
Total revenues	501.7	450.7	941.1	832.7
Xywav
Disaggregation of Revenue [Line Items]
Total revenues	471.2	415.3	879.4	760.1
Xyrem
Disaggregation of Revenue [Line Items]
Total revenues	30.5	35.4	61.7	72.6
Epilepsy
Disaggregation of Revenue [Line Items]
Total revenues	292.1	251.7	541.9	469.4
Epidiolex/Epidyolex
Disaggregation of Revenue [Line Items]
Total revenues	292.1	251.7	541.9	469.4
Oncology
Disaggregation of Revenue [Line Items]
Total revenues	362.3	274.7	695.7	504.1
Zepzelca
Disaggregation of Revenue [Line Items]
Total revenues	105.8	74.5	206.8	137.5
Rylaze/Enrylaze
Disaggregation of Revenue [Line Items]
Total revenues	99.5	100.7	203.2	194.9
Defitelio/defibrotide
Disaggregation of Revenue [Line Items]
Total revenues	62.0	48.1	109.4	88.8
Modeyso
Disaggregation of Revenue [Line Items]
Total revenues	48.2	0.5	89.6	0.5
Vyxeos
Disaggregation of Revenue [Line Items]
Total revenues	31.4	44.9	58.0	74.4
Ziihera
Disaggregation of Revenue [Line Items]
Total revenues	15.4	6.0	28.7	8.0
Other
Disaggregation of Revenue [Line Items]
Total revenues	0.0	8.5	2.7	18.8
High-sodium oxybate AG royalty revenue
Disaggregation of Revenue [Line Items]
Total revenues	42.2	54.1	78.5	103.0
Other royalty and contract revenues
Disaggregation of Revenue [Line Items]
Total revenues	$ 10.0	$ 6.0	$ 17.3	$ 15.5