Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Details) $ in Millions	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Equity warrant assets (public portfolio) | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 2	$ 1
Equity warrant assets (public portfolio) | Volatility | Lower Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.278	0.460
Equity warrant assets (public portfolio) | Volatility | Upper Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.550	0.568
Equity warrant assets (public portfolio) | Volatility | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.011	0.491
Equity warrant assets (public portfolio) | Risk-Free Interest Rate | Lower Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.006	0.003
Equity warrant assets (public portfolio) | Risk-Free Interest Rate | Upper Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.015	0.009
Equity warrant assets (public portfolio) | Risk-Free Interest Rate | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.107	0.006
Equity warrant assets (public portfolio) | Sales restrictions discount | Lower Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.10	0.100
Equity warrant assets (public portfolio) | Sales restrictions discount | Upper Limit
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.20
Equity warrant assets (public portfolio) | Sales restrictions discount | Upper Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.20	0.200
Equity warrant assets (public portfolio) | Sales restrictions discount | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.437	0.102
Equity warrant assets (private portfolio) | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 267	$ 191
Equity warrant assets (private portfolio) | Volatility | Lower Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.247	0.244
Equity warrant assets (private portfolio) | Volatility | Upper Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.550	0.568
Equity warrant assets (private portfolio) | Volatility | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.430	0.432
Equity warrant assets (private portfolio) | Risk-Free Interest Rate | Lower Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.0006	0.0001
Equity warrant assets (private portfolio) | Risk-Free Interest Rate | Upper Limit | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.014	0.0052
Equity warrant assets (private portfolio) | Risk-Free Interest Rate | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.008	0.001
Equity warrant assets (private portfolio) | Marketability discount | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	20.1	20.6
Equity warrant assets (private portfolio) | Marketability discount | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.201	0.206
Equity warrant assets (private portfolio) | Remaining life assumption | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	40	40
Equity warrant assets (private portfolio) | Remaining life assumption | Weighted average | Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Weighted Average	0.400	0.400