Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2010 cvr	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Sep. 18, 2023 position
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset Statement Of Financial Position Extensible Enumeration Not Disclosed Flag		Derivative assets(2)	Derivative assets(2)
Number of CVR Series | cvr	4
Primrose Bio
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest in potential development milestone (as a percent)				50.00%
Primordial Genetics
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of contracts | position				2
Transferred over Time | Phase 3 clinical trial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross contract asset		$ 10,000
Maximum | Transferred over Time | Development, regulatory, & commercial milestones and tiered royalties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		375,000
Metabasis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of CVRs issued per acquiree share | cvr	4
Number of CVRs issued from each CVR series | cvr	1
Frequency of cash payments to CVR holders	6 months
(Decrease) increase of mark-to-market adjustment of CVR liability		(100)
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Viking common stock		82,000	$ 32,185
Derivative asset		3,727	3,531
Total assets		264,227	150,886
Total liabilities		3,015	3,198
Recurring | Short-term investments, excluding Viking
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		178,500	115,170
Recurring | Contingent liabilities | CyDex
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		218	320
Recurring | Contingent liabilities | Metabasis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		2,797	2,878
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Viking common stock		82,000	32,185
Derivative asset		0	0
Total assets		97,663	39,476
Total liabilities		0	0
Recurring | Level 1 | Short-term investments, excluding Viking
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		15,663	7,291
Recurring | Level 1 | Contingent liabilities | CyDex
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		0	0
Recurring | Level 1 | Contingent liabilities | Metabasis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		0	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Viking common stock		0	0
Derivative asset		0	0
Total assets		162,837	107,879
Total liabilities		2,797	2,878
Recurring | Level 2 | Short-term investments, excluding Viking
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		162,837	107,879
Recurring | Level 2 | Contingent liabilities | CyDex
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		0	0
Recurring | Level 2 | Contingent liabilities | Metabasis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		2,797	2,878
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in Viking common stock		0	0
Derivative asset		3,727	3,531
Total assets		3,727	3,531
Total liabilities		218	320
Recurring | Level 3 | Short-term investments, excluding Viking
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value		0	0
Recurring | Level 3 | Contingent liabilities | CyDex
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		218	320
Recurring | Level 3 | Contingent liabilities | Metabasis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent liabilities		$ 0	$ 0