Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Additional Information) (Details)	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Weighted average remaining life	2 years 7 months 6 days
Weighted average remaining life	6 years 7 months 6 days
Sales restrictions discount | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.100
Sales restrictions discount | Lower Limit | Other equity securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.10
Sales restrictions discount | Lower Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.10	0.100
Sales restrictions discount | Upper Limit | Other equity securities
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.20
Sales restrictions discount | Upper Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.20	0.200
Sales restrictions discount | Weighted Average | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.100	0.102
Volatility | Lower Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.474	0.460
Volatility | Lower Limit | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.250	0.244
Volatility | Upper Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input		0.568
Volatility | Upper Limit | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.580	0.568
Volatility | Weighted Average | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.474	0.491
Volatility | Weighted Average | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.457	0.432
Risk-Free interest rate | Lower Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.009	0.003
Risk-Free interest rate | Lower Limit | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.0001	0.0001
Risk-Free interest rate | Upper Limit | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.016	0.009
Risk-Free interest rate | Upper Limit | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.0117	0.0052
Risk-Free interest rate | Weighted Average | Level 3 | Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.011	0.006
Risk-Free interest rate | Weighted Average | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.003	0.001
Marketability discount | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.217	0.2063
Marketability discount | Weighted Average | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.217	0.206
Remaining life assumption | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.400	0.400
Remaining life assumption | Weighted Average | Level 3 | Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.400	0.400