Amortized Cost or Cost, Gross Unrealized Gains (Losses) and Fair Value of Fixed Maturity and Equity Securities Classified as Available-for-Sale (Detail) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	$ 51,248	$ 52,611
Fair value, fixed maturity securities	49,286	60,480
Fixed maturity securities
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	51,248	52,611
Gross unrealized gains, fixed maturity securities	1,343	8,004
Gross unrealized losses, fixed maturity securities	(3,305)	(135)
Allowance for credit losses	0	0	$ 0	$ (3)	$ (4)
Fair value, fixed maturity securities	49,286	60,480
Fixed maturity securities | U.S. government, agencies and government-sponsored enterprises
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	3,387	3,368
Gross unrealized gains, fixed maturity securities	274	1,184
Gross unrealized losses, fixed maturity securities	(34)	0
Allowance for credit losses	0	0
Fair value, fixed maturity securities	3,627	4,552
Fixed maturity securities | State and Political Subdivisions
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,971	2,982
Gross unrealized gains, fixed maturity securities	74	474
Gross unrealized losses, fixed maturity securities	(196)	(6)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	2,849	3,450
Fixed maturity securities | Non-U.S. government
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	762	762
Gross unrealized gains, fixed maturity securities	17	86
Gross unrealized losses, fixed maturity securities	(97)	(13)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	682	835
Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	29,566	30,257
Gross unrealized gains, fixed maturity securities	733	4,746
Gross unrealized losses, fixed maturity securities	(2,056)	(79)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	28,243	34,924
Fixed maturity securities | U.S. corporate | Utilities
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	4,253	4,330
Gross unrealized gains, fixed maturity securities	135	783
Gross unrealized losses, fixed maturity securities	(285)	(9)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	4,103	5,104
Fixed maturity securities | U.S. corporate | Energy
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,496	2,581
Gross unrealized gains, fixed maturity securities	54	363
Gross unrealized losses, fixed maturity securities	(173)	(10)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	2,377	2,934
Fixed maturity securities | U.S. corporate | Finance and insurance
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	7,947	8,003
Gross unrealized gains, fixed maturity securities	126	1,012
Gross unrealized losses, fixed maturity securities	(604)	(24)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	7,469	8,991
Fixed maturity securities | U.S. corporate | Consumer-non-cyclical
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	4,912	5,138
Gross unrealized gains, fixed maturity securities	172	1,029
Gross unrealized losses, fixed maturity securities	(292)	(8)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	4,792	6,159
Fixed maturity securities | U.S. corporate | Technology and communications
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	3,224	3,345
Gross unrealized gains, fixed maturity securities	60	476
Gross unrealized losses, fixed maturity securities	(260)	(13)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	3,024	3,808
Fixed maturity securities | U.S. corporate | Industrial
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,263	1,322
Gross unrealized gains, fixed maturity securities	22	175
Gross unrealized losses, fixed maturity securities	(98)	(3)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	1,187	1,494
Fixed maturity securities | U.S. corporate | Capital goods
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,326	2,334
Gross unrealized gains, fixed maturity securities	77	415
Gross unrealized losses, fixed maturity securities	(145)	(4)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	2,258	2,745
Fixed maturity securities | U.S. corporate | Consumer-cyclical
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,679	1,703
Gross unrealized gains, fixed maturity securities	27	203
Gross unrealized losses, fixed maturity securities	(125)	(7)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	1,581	1,899
Fixed maturity securities | U.S. corporate | Transportation
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,113	1,122
Gross unrealized gains, fixed maturity securities	52	249
Gross unrealized losses, fixed maturity securities	(61)	0
Allowance for credit losses	0	0
Fair value, fixed maturity securities	1,104	1,371
Fixed maturity securities | U.S. corporate | Other
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	353	379
Gross unrealized gains, fixed maturity securities	8	41
Gross unrealized losses, fixed maturity securities	(13)	(1)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	348	419
Fixed maturity securities | Non-U.S. corporate
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	8,905	9,344
Gross unrealized gains, fixed maturity securities	201	1,217
Gross unrealized losses, fixed maturity securities	(624)	(26)
Allowance for credit losses	0	0	0	$ (3)	(1)
Fair value, fixed maturity securities	8,482	10,535
Fixed maturity securities | Non-U.S. corporate | Utilities
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	864	867
Gross unrealized gains, fixed maturity securities	3	63
Gross unrealized losses, fixed maturity securities	(57)	(2)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	810	928
Fixed maturity securities | Non-U.S. corporate | Energy
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,123	1,194
Gross unrealized gains, fixed maturity securities	36	190
Gross unrealized losses, fixed maturity securities	(62)	(1)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	1,097	1,383
Fixed maturity securities | Non-U.S. corporate | Finance and insurance
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,103	2,171
Gross unrealized gains, fixed maturity securities	62	270
Gross unrealized losses, fixed maturity securities	(153)	(9)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	2,012	2,432
Fixed maturity securities | Non-U.S. corporate | Consumer-non-cyclical
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	630	664
Gross unrealized gains, fixed maturity securities	4	81
Gross unrealized losses, fixed maturity securities	(64)	(2)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	570	743
Fixed maturity securities | Non-U.S. corporate | Technology and communications
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,007	1,085
Gross unrealized gains, fixed maturity securities	10	166
Gross unrealized losses, fixed maturity securities	(74)	(1)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	943	1,250
Fixed maturity securities | Non-U.S. corporate | Industrial
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	903	933
Gross unrealized gains, fixed maturity securities	21	117
Gross unrealized losses, fixed maturity securities	(63)	(3)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	861	1,047
Fixed maturity securities | Non-U.S. corporate | Capital goods
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	609	640
Gross unrealized gains, fixed maturity securities	6	66
Gross unrealized losses, fixed maturity securities	(50)	(1)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	565	705
Fixed maturity securities | Non-U.S. corporate | Consumer-cyclical
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	314	316
Gross unrealized gains, fixed maturity securities	0	27
Gross unrealized losses, fixed maturity securities	(29)	(2)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	285	341
Fixed maturity securities | Non-U.S. corporate | Transportation
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	392	422
Gross unrealized gains, fixed maturity securities	20	68
Gross unrealized losses, fixed maturity securities	(22)	(1)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	390	489
Fixed maturity securities | Non-U.S. corporate | Other
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	960	1,052
Gross unrealized gains, fixed maturity securities	39	169
Gross unrealized losses, fixed maturity securities	(50)	(4)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	949	1,217
Fixed maturity securities | Residential mortgage-backed
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	1,214	1,325
Gross unrealized gains, fixed maturity securities	36	116
Gross unrealized losses, fixed maturity securities	(37)	(1)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	1,213	1,440
Fixed maturity securities | Commercial mortgage-backed
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,272	2,435
Gross unrealized gains, fixed maturity securities	7	152
Gross unrealized losses, fixed maturity securities	(142)	(3)
Allowance for credit losses	0	0	$ 0		$ (3)
Fair value, fixed maturity securities	2,137	2,584
Fixed maturity securities | Other asset-backed
Schedule of Investments [Line Items]
Amortized cost or cost, fixed maturity securities	2,171	2,138
Gross unrealized gains, fixed maturity securities	1	29
Gross unrealized losses, fixed maturity securities	(119)	(7)
Allowance for credit losses	0	0
Fair value, fixed maturity securities	$ 2,053	$ 2,160