Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Details) - Level 3 $ in Millions	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Equity warrant assets | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1	$ 2
Equity warrant assets | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	314	$ 267
Contingent conversion rights | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	2
Contingent conversion rights | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 5
Volatility | Equity warrant assets | Lower Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.450	0.278
Volatility | Equity warrant assets | Lower Limit | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.241	0.247
Volatility | Equity warrant assets | Upper Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.532	0.550
Volatility | Equity warrant assets | Upper Limit | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.532	0.550
Volatility | Equity warrant assets | Weighted Average | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.023	0.011
Volatility | Equity warrant assets | Weighted Average | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.425	0.430
Volatility | Contingent conversion rights | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.532
Volatility | Contingent conversion rights | Weighted Average | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.021
Risk-Free interest rate | Equity warrant assets | Lower Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.023	0.006
Risk-Free interest rate | Equity warrant assets | Lower Limit | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.0052	0.0006
Risk-Free interest rate | Equity warrant assets | Upper Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.024	0.015
Risk-Free interest rate | Equity warrant assets | Upper Limit | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.0245	0.0140
Risk-Free interest rate | Equity warrant assets | Weighted Average | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.200	0.107
Risk-Free interest rate | Equity warrant assets | Weighted Average | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.021	0.008
Risk-Free interest rate | Contingent conversion rights | Lower Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.0212
Risk-Free interest rate | Contingent conversion rights | Upper Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.0232
Risk-Free interest rate | Contingent conversion rights | Weighted Average | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.200
Sales restrictions discount | Equity warrant assets | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.200
Sales restrictions discount | Equity warrant assets | Lower Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input		0.100
Sales restrictions discount | Equity warrant assets | Upper Limit | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input		0.200
Sales restrictions discount | Equity warrant assets | Weighted Average | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.517	0.437
Sales restrictions discount | Contingent conversion rights | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	20.0
Sales restrictions discount | Contingent conversion rights | Weighted Average | Public Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.532
Marketability discount | Equity warrant assets | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.188	0.201
Marketability discount | Equity warrant assets | Weighted Average | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.188	0.201
Remaining life assumption | Equity warrant assets | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.400	0.400
Remaining life assumption | Equity warrant assets | Weighted Average | Private Portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Measurement input	0.400	0.400