Fair Value Measurement of Assets and Liabilities - Assets Measured Valued Using Unobservable Inputs (Details) - Fair Value, Measurements, Recurring - Significant  Unobservable Inputs (Level 3) - Warrant - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening balance at beginning of period	$ 281	$ 148
Change in fair value	770	133
Closing balance at end of period	$ 1,051	$ 281