Separate Account Assets and Liabilities - Separate Account Assets (Details) - Life and Retirement - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Separate Account Investment [Line Items]
Value of investment options	$ 95,173	$ 91,005
Individual Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	49,938	47,893
Group Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	40,065	38,188
Life Insurance
Fair Value, Separate Account Investment [Line Items]
Value of investment options	1,016	932
Institutional Markets
Fair Value, Separate Account Investment [Line Items]
Value of investment options	4,154	3,992
Equity funds | Equity funds
Fair Value, Separate Account Investment [Line Items]
Value of investment options	58,765	55,538
Equity funds | Equity funds | Individual Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	26,945	25,451
Equity funds | Equity funds | Group Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	30,285	28,675
Equity funds | Equity funds | Life Insurance
Fair Value, Separate Account Investment [Line Items]
Value of investment options	900	819
Equity funds | Equity funds | Institutional Markets
Fair Value, Separate Account Investment [Line Items]
Value of investment options	635	593
Bond funds | Bond funds
Fair Value, Separate Account Investment [Line Items]
Value of investment options	8,762	8,676
Bond funds | Bond funds | Individual Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	4,121	4,037
Bond funds | Bond funds | Group Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	3,315	3,292
Bond funds | Bond funds | Life Insurance
Fair Value, Separate Account Investment [Line Items]
Value of investment options	45	44
Bond funds | Bond funds | Institutional Markets
Fair Value, Separate Account Investment [Line Items]
Value of investment options	1,281	1,303
Balanced funds | Balanced funds
Fair Value, Separate Account Investment [Line Items]
Value of investment options	25,959	25,166
Balanced funds | Balanced funds | Individual Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	18,179	17,711
Balanced funds | Balanced funds | Group Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	5,663	5,479
Balanced funds | Balanced funds | Life Insurance
Fair Value, Separate Account Investment [Line Items]
Value of investment options	55	53
Balanced funds | Balanced funds | Institutional Markets
Fair Value, Separate Account Investment [Line Items]
Value of investment options	2,062	1,923
Money market funds | Money market funds
Fair Value, Separate Account Investment [Line Items]
Value of investment options	1,687	1,625
Money market funds | Money market funds | Individual Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	693	694
Money market funds | Money market funds | Group Retirement
Fair Value, Separate Account Investment [Line Items]
Value of investment options	802	742
Money market funds | Money market funds | Life Insurance
Fair Value, Separate Account Investment [Line Items]
Value of investment options	16	16
Money market funds | Money market funds | Institutional Markets
Fair Value, Separate Account Investment [Line Items]
Value of investment options	$ 176	$ 173