Cumulative Allowance and the Provision for Changes in Expected Cash Flows from Financial Royalty Assets - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Line Items]
Cumulative adjustment to retained earnings	$ (9,895,815)	$ (6,141,438)	$ (4,552,079)	$ (4,460,546)
Retained Earnings
Financing Receivable, Allowance for Credit Loss [Line Items]
Cumulative adjustment to retained earnings	$ (1,920,635)	(2,825,212)	$ (1,215,953)	(655,446)
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Line Items]
Cumulative adjustment to retained earnings		192,705		0
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
Financing Receivable, Allowance for Credit Loss [Line Items]
Cumulative adjustment to retained earnings		$ 192,705		$ 2,863