Special Purpose Entities, Including Variable Interest Entities - Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 2,972	$ 3,187
Investments:
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	113	132
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 20	$ 5