Contracts Accounted for as Credit Derivatives - Net Change in Fair Value of Credit Derivatives Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Realized gains on credit derivatives	$ 1	$ 2
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	0	(2)
Realized gains (losses) and other settlements	1	0
Net unrealized gains (losses)	(20)	(77)
Net change in fair value of credit derivatives	$ (19)	$ (77)