Derivative Financial Instruments and Off-balance Sheet Financial Instruments - OTC derivatives counterparty credit exposure by counterparty credit rating (Details) $ in Millions	Dec. 31, 2022 USD ($) counter-party	Dec. 31, 2021 USD ($) counter-party
Credit Derivatives
Number of counter-parties | counter-party	2	2
Notional amount	$ 320	$ 566
Credit exposure	12	16
Exposure, net of collateral	$ 0	$ 0
A+
Credit Derivatives
Number of counter-parties | counter-party	1	1
Notional amount	$ 128	$ 199
Credit exposure	5	7
Exposure, net of collateral	$ 0	$ 0
A
Credit Derivatives
Number of counter-parties | counter-party	1	1
Notional amount	$ 192	$ 367
Credit exposure	7	9
Exposure, net of collateral	$ 0	$ 0