Investments - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) Security	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) fund Security manager	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) Security
Schedule of Investments [Line Items]
Number of outside managers managing investment portfolio | manager			3
Funds accounted for as CIVs | fund			3
Total number of investments | fund			6
Accrued investment income	$ 78		$ 78		$ 71
Number of securities with unrealized losses greater than 10% of book value for 12 months or more | Security	641		641		567
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more	$ 351		$ 351		$ 329
Assets held-in-trust	224		224		222
Allowance for credit loss	(8)	$ (4)	(23)	$ (13)
Sales	73	207	767	$ 560
Securities purchased with credit deterioration	0	22	0
Securities purchased with credit deterioration, amount at par value		31
Allowance for credit loss at acquisition date		2
Discount attributable to other factors		$ 7
Disposal Group, Held-for-sale, Not Discontinued Operations | Sound Point Agreement
Schedule of Investments [Line Items]
Transaction commitment, new and transitioned investments	1,000
AGL Subsidiaries
Schedule of Investments [Line Items]
Assets held-in-trust	1,107		1,107		$ 1,169
Future Equity Investments | Alternative Investment
Schedule of Investments [Line Items]
Investments, including distributed gains, authorized amount to invest	132		132
Investments, authorized amount to invest	1,500		1,500
Investments, fair value disclosure	630		630
Unfunded committment	890		890
Unfunded committment, committed for specific funds	332		332
Future Equity Investments | AGL Subsidiaries | Alternative Investment
Schedule of Investments [Line Items]
Investments, authorized amount to invest	882		882
Authorized amount to invest, excluding distributed gains	750		750
Equity in Earnings (Losses) of Investees | AGAS | Alternative Investment
Schedule of Investments [Line Items]
Investments, fair value disclosure	469		469
Long-term purchase commitment, amount			703
Funded amount	$ 446		$ 446