Derivative Financial Instruments and Off-balance sheet Financial Instruments - OTC derivatives counterparty credit exposure (Details)	Dec. 31, 2021 USD ($) counter-party	Dec. 31, 2020 USD ($) counter-party
Credit Derivatives
Number of counter-parties | counter-party	2	1
Notional amount	$ 566,000,000	$ 186,000,000
Credit exposure	16,000,000	4,000,000
Exposure, net of collateral	0	0
Gross liability fair value of contracts containing credit-risk-contingent features	8,000,000	19,000,000
Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs	(7,000,000)	(6,000,000)
Collateral posted under MNAs for contracts containing credit-risk-contingent features	0	(13,000,000)
Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently	$ 1,000,000	$ 0
A plus
Credit Derivatives
Number of counter-parties | counter-party	1	1
Notional amount	$ 199,000,000	$ 186,000,000
Credit exposure	7,000,000	4,000,000
Exposure, net of collateral	$ 0	$ 0
A
Credit Derivatives
Number of counter-parties | counter-party	1	0
Notional amount	$ 367,000,000	$ 0
Credit exposure	9,000,000	0
Exposure, net of collateral	$ 0	$ 0