Basis of Presentation and Summary of Significant Accounting Policies - Revenue by Source (Details) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended		9 Months Ended
	Mar. 06, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenue		$ 24,808	$ 45,663	$ 93,279	$ 191,863
Royalties
Disaggregation of Revenue [Line Items]
Total revenue		9,767	36,127	35,931	88,343
Promacta
Disaggregation of Revenue [Line Items]
Total revenue	$ 14,200	0	27,812	14,193	68,191
Kyprolis
Disaggregation of Revenue [Line Items]
Total revenue		7,602	6,286	16,317	14,411
Evomela
Disaggregation of Revenue [Line Items]
Total revenue		1,515	1,356	3,570	4,116
Other
Disaggregation of Revenue [Line Items]
Total revenue		650	673	1,851	1,625
Material Sales: Captisol
Disaggregation of Revenue [Line Items]
Total revenue		6,849	7,027	24,357	19,030
License fees, milestones and other
Disaggregation of Revenue [Line Items]
Total revenue		8,192	2,509	32,991	84,490
License Fees
Disaggregation of Revenue [Line Items]
Total revenue		243	265	3,083	75,201
Milestone
Disaggregation of Revenue [Line Items]
Total revenue		4,790	1,308	20,897	6,052
Other
Disaggregation of Revenue [Line Items]
Total revenue		$ 3,159	$ 936	$ 9,011	$ 3,237