Special Purpose Entities, Including Variable Interest Entities - Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Variable Interest Entities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 2,100	$ 2,041
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	27	31
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	122	106
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Loans Unpaid Principal Balance	1,756	1,977
Long Term Debt Unpaid Principal Balance	2,857	3,064
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member]
Variable Interest Entities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 94	$ 99