Variable Interest Entities - Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entities [Line Items]
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	$ 2,314	$ 2,247
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	1,122	1,083
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	27,998	31,506
Investments:
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	8
Fixed income securities, amortized cost	2,807	3,187
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	149	132
Variable Interest Entity [Member]
Investments:
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities		7
Municipal Bonds [Member] | Variable Interest Entity [Member]
Investments:
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	$ 27	$ 25