Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Additional Information) (Details)	3 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average remaining life	6 years 7 months 6 days
Weighted average remaining life	2 years 7 months 6 days
Sales restrictions discount | Upper Limit | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.20
Level 3 | Lower Limit | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value inputs, sales restriction, period	3 months
Level 3 | Upper Limit | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value inputs, sales restriction, period	6 months
Level 3 | Sales restrictions discount | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.100
Level 3 | Sales restrictions discount | Lower Limit | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.10	0.100
Level 3 | Sales restrictions discount | Upper Limit | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.20	0.200