Contracts Accounted for as Credit Derivatives - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) Counterparty	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Credit Derivatives
Net Par Outstanding	$ 5,806	$ 5,956
Credit risk derivatives, at fair value, net	(262)	(185)
Net expected loss to be paid after recoveries	$ 660	$ 737	$ 963	$ 1,183
Estimated remaining weighted average life of credit derivatives (in years)	11 years 3 months 18 days	11 years 6 months
Gross par of CDS with collateral posting requirement [Member]
Credit Derivatives
Collateral posting requirement	$ 168
Number of counterparties | Counterparty	1