Fair Value Measurements - Fair Value Inputs, Liabilities, Quantitative Information (Details) - Fair Value, Inputs, Level 3	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Revenue-based royalty
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration liabilities	$ 4,804,000	$ 7,710,000
Revenue milestones
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration liabilities	55,561,000	66,114,000
Regulatory approval
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration liabilities	$ 4,300,000	$ 2,885,000
Discount rate | Revenue-based royalty | Minimum | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.13	0.13
Discount rate | Revenue-based royalty | Maximum | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.20	0.24
Discount rate | Revenue-based royalty | Weighted Average | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.136
Discount rate | Revenue milestones | Minimum | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.11	0.09
Discount rate | Revenue milestones | Maximum | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.14	0.135
Discount rate | Revenue milestones | Weighted Average | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.124
Discount rate | Regulatory approval | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.027	0.024
Probability of milestone payment | Regulatory approval | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable inputs, contingent liability	0.90	0.65