Derivative Financial Instruments - CDS notional amount by credit rating and fair value of protection sold (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Term of credit default swaps (in years)	5 years
Derivative [Line Items]
Notional amount	$ 2,145	$ 2,075
Credit default contracts
Derivative [Line Items]
Notional amount	5	255
Fair value	0	6
Single name | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	5	5
Fair value	0	0
Index | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	250
Fair value	0	6
AAA | Credit default contracts
Derivative [Line Items]
Notional amount	0	2
AAA | Single name | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	0
AAA | Index | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	2
AA | Credit default contracts
Derivative [Line Items]
Notional amount	0	4
AA | Single name | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	0
AA | Index | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	4
A | Credit default contracts
Derivative [Line Items]
Notional amount	0	46
A | Single name | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	0
A | Index | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	46
BBB | Credit default contracts
Derivative [Line Items]
Notional amount	0	190
BBB | Single name | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	0
BBB | Index | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	0	190
BB and lower | Credit default contracts
Derivative [Line Items]
Notional amount	5	13
BB and lower | Single name | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	5	5
BB and lower | Index | Corporate | Credit default contracts
Derivative [Line Items]
Notional amount	$ 0	$ 8