Fair Value of Financial Instruments - Additional Information about Level 3 Assets Measured at Fair Value on a Recurring Basis (Details) - Measured on a recurring basis - Fair value accounting - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 146,278	$ 122,250	$ 130,853
Total Realized and Unrealized Gains (Losses) Included in Income	133,922	88,439	55,234
Purchases	575	0	0
Sales/Exits	(131,352)	(78,752)	(76,861)
Issuances	16,453	17,941	14,537
Distributions and Other Settlements	3	(297)	0
Transfers Out of Level 3	(4,707)	(3,303)	(1,513)
Ending Balance	161,172	146,278	122,250
Equity warrant assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	145,199	121,331	128,813
Total Realized and Unrealized Gains (Losses) Included in Income	133,910	87,982	54,263
Purchases	575	0	0
Sales/Exits	(130,392)	(78,752)	(74,769)
Issuances	16,453	17,941	14,537
Distributions and Other Settlements	0	0	0
Transfers Out of Level 3	(4,707)	(3,303)	(1,513)
Ending Balance	161,038	145,199	121,331
Non-marketable securities | Unconsolidated venture capital and private equity fund investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,079	919	2,040
Total Realized and Unrealized Gains (Losses) Included in Income	12	457	971
Purchases	0	0	0
Sales/Exits	(960)	0	(2,092)
Issuances	0	0	0
Distributions and Other Settlements	3	(297)	0
Transfers Out of Level 3	0	0	0
Ending Balance	$ 134	$ 1,079	$ 919