Investments - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 2	$ 3	$ 1
Securities fair value	23	24
Debt Securities, Available-for-sale, Unrealized Loss Position	1,145	1,032
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	75	71
Debt Securities, Available for sale, Unrealized Loss Position, Accumulated Loss, Including Pledged Securities	$ 1,172
Average Percentage of Unrealized Loss Versus Amortized Cost for Below Investment Grade Securities	5.00%
Average Percentage of Unrealized Loss Versus Amortized Cost for Investment Grade Securities	7.00%
Fiduciary Funds Held by Insurance Distribution Subsidiaries	$ 2	2
Investment Portfolio [Member]
Schedule of Investments [Line Items]
Fair Value of Cash and Securities Pledged to Derivative Counterparties	26	27
Fixed Income Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	2	3
Debt Securities, Available-for-sale, Unrealized Loss Position	1,101	1,028
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	74	71
Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	596	584
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	45	44
Fixed Income Securities [Member] | Corporate Debt Securities [Member] | External Credit Rating, Investment Grade
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	45
Fixed Income Securities [Member] | Corporate Debt Securities [Member] | External Credit Rating, Non Investment Grade [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	2	3
Debt Securities, Available-for-sale, Unrealized Loss Position	153	104
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	12	14
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	132	92
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5	1
Reported Value Measurement [Member]
Schedule of Investments [Line Items]
Other investments	152	77
Reported Value Measurement [Member] | Interest Rate Contract [Member]
Schedule of Investments [Line Items]
Other investments	$ 95	$ 39