Derivative Financial Instruments - OTC derivatives counterparty credit exposure by counterparty credit rating (Details) $ in Millions	Mar. 31, 2022 USD ($) counter-party	Dec. 31, 2021 USD ($) counter-party
Credit Derivatives
Number of counter- parties | counter-party	3	2
Notional amount	$ 728	$ 566
Credit exposure	24	16
Exposure, net of collateral	$ 2	$ 0
A+
Credit Derivatives
Number of counter- parties | counter-party	2	1
Notional amount	$ 401	$ 199
Credit exposure	11	7
Exposure, net of collateral	$ 2	$ 0
A
Credit Derivatives
Number of counter- parties | counter-party	1	1
Notional amount	$ 327	$ 367
Credit exposure	13	9
Exposure, net of collateral	$ 0	$ 0