Fair Value Measurements - Assets and Liabilities at Fair Value (Details) - USD ($)	3 Months Ended
	Sep. 30, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets:
Short-term investments	$ 874,383,000		$ 601,217,000
Investment in Viking common stock	41,542,000		46,191,000
Investment in warrants	8,314,000		9,257,000
Total assets	924,239,000		656,665,000
Liabilities:
Amounts owed to former licensor	61,000		199,000
Total liabilities	9,850,000		12,741,000
Repayments of related party debt	3,000,000.0	$ 1,000,000.0
Transferred over Time | Phase 3 Clinical Trial
Liabilities:
Contract asset	10,000,000
Maximum | Transferred over Time | Development, Regulatory, & Commercial Milestones and Tiered Royalties
Liabilities:
Investments	375,000,000
Crystal
Liabilities:
Contingent liabilities	1,826,000		6,477,000
CyDex
Liabilities:
Contingent liabilities	465,000		514,000
Metabasis
Liabilities:
Contingent liabilities	7,498,000		5,551,000
Level 1
Assets:
Short-term investments	2,171,000		1,326,000
Investment in Viking common stock	41,542,000		46,191,000
Investment in warrants	8,314,000		9,257,000
Total assets	52,027,000		56,774,000
Liabilities:
Amounts owed to former licensor	61,000		199,000
Total liabilities	61,000		199,000
Level 1 | Crystal
Liabilities:
Contingent liabilities	0		0
Level 1 | CyDex
Liabilities:
Contingent liabilities	0		0
Level 1 | Metabasis
Liabilities:
Contingent liabilities	0		0
Level 2
Assets:
Short-term investments	872,147,000		599,891,000
Investment in Viking common stock	0		0
Investment in warrants	0		0
Total assets	872,147,000		599,891,000
Liabilities:
Amounts owed to former licensor	0		0
Total liabilities	7,498,000		5,551,000
Level 2 | Crystal
Liabilities:
Contingent liabilities	0		0
Level 2 | CyDex
Liabilities:
Contingent liabilities	0		0
Level 2 | Metabasis
Liabilities:
Contingent liabilities	7,498,000		5,551,000
Level 3
Assets:
Short-term investments	65,000		0
Investment in Viking common stock	0		0
Investment in warrants	0		0
Total assets	65,000		0
Liabilities:
Amounts owed to former licensor	0		0
Total liabilities	2,291,000		6,991,000
Level 3 | Crystal
Liabilities:
Contingent liabilities	1,826,000		6,477,000
Level 3 | CyDex
Liabilities:
Contingent liabilities	465,000		514,000
Level 3 | Metabasis
Liabilities:
Contingent liabilities	$ 0		$ 0