Estimated Fair Value of Financial Instruments - Fair Value Measurements and Valuation Techniques (Details) - Fair Value, Recurring - Discounted Cash Flow - Level 3 $ in Thousands	Mar. 31, 2020 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Liability related to sale of future royalties	$ 274,706
Minimum | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Future royalty sale, liability, measurement input	16.00%
Maximum | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Future royalty sale, liability, measurement input	26.00%
Weighted Average | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Future royalty sale, liability, measurement input	19.00%