Gross Unrealized Losses and Fair Value of Investment Securities (Detail) $ in Millions	Jun. 30, 2022 USD ($) Securities	Dec. 31, 2021 USD ($) Securities
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 30,227	$ 4,991
Less than 12 months, Gross unrealized losses	$ (3,039)	$ (110)
Less than 12 months, Number of securities in a continuous loss position | Securities	4,016	635
12 months or more, Fair value	$ 1,102	$ 308
12 months or more, Gross unrealized losses	$ (266)	$ (25)
12 months or more, Number of securities in a continuous loss position | Securities	157	35
Fair value	$ 31,329	$ 5,299
Gross unrealized losses	$ (3,305)	$ (135)
Number of securities in a continuous loss position | Securities	4,173	670
Investment grade
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 28,568	$ 4,644
Less than 12 months, Gross unrealized losses	$ (2,801)	$ (101)
Less than 12 months, Number of securities in a continuous loss position | Securities	3,763	587
12 months or more, Fair value	$ 1,023	$ 241
12 months or more, Gross unrealized losses	$ (241)	$ (12)
12 months or more, Number of securities in a continuous loss position | Securities	144	25
Fair value	$ 29,591	$ 4,885
Gross unrealized losses	$ (3,042)	$ (113)
Number of securities in a continuous loss position | Securities	3,907	612
Below investment grade
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 1,659	$ 347
Less than 12 months, Gross unrealized losses	$ (238)	$ (9)
Less than 12 months, Number of securities in a continuous loss position | Securities	253	48
12 months or more, Fair value	$ 79	$ 67
12 months or more, Gross unrealized losses	$ (25)	$ (13)
12 months or more, Number of securities in a continuous loss position | Securities	13	10
Fair value	$ 1,738	$ 414
Gross unrealized losses	$ (263)	$ (22)
Number of securities in a continuous loss position | Securities	266	58
Fixed maturity securities
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 30,227	$ 4,991
Less than 12 months, Gross unrealized losses	$ (3,039)	$ (110)
Less than 12 months, Number of securities in a continuous loss position | Securities	4,016	635
12 months or more, Fair value	$ 1,102	$ 308
12 months or more, Gross unrealized losses	$ (266)	$ (25)
12 months or more, Number of securities in a continuous loss position | Securities	157	35
Fair value	$ 31,329	$ 5,299
Gross unrealized losses	$ (3,305)	$ (135)
Number of securities in a continuous loss position | Securities	4,173	670
Fixed maturity securities | Less Than 20 Percent Below Cost
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 28,164	$ 4,991
Less than 12 months, Gross unrealized losses	$ (2,402)	$ (110)
Less than 12 months, Number of securities in a continuous loss position | Securities	3,756	635
12 months or more, Fair value	$ 627	$ 297
12 months or more, Gross unrealized losses	$ (101)	$ (20)
12 months or more, Number of securities in a continuous loss position | Securities	98	33
Fair value	$ 28,791	$ 5,288
Gross unrealized losses	$ (2,503)	$ (130)
Number of securities in a continuous loss position | Securities	3,854	668
Fixed maturity securities | 20 To 50 percent below cost
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 2,063	$ 0
Less than 12 months, Gross unrealized losses	$ (637)	$ 0
Less than 12 months, Number of securities in a continuous loss position | Securities	260	0
12 months or more, Fair value	$ 475	$ 11
12 months or more, Gross unrealized losses	$ (165)	$ (5)
12 months or more, Number of securities in a continuous loss position | Securities	59	2
Fair value	$ 2,538	$ 11
Gross unrealized losses	$ (802)	$ (5)
Number of securities in a continuous loss position | Securities	319	2
Fixed maturity securities | U.S. government, agencies and government-sponsored enterprises
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 797
Less than 12 months, Gross unrealized losses	$ (33)
Less than 12 months, Number of securities in a continuous loss position | Securities	49
12 months or more, Fair value	$ 10
12 months or more, Gross unrealized losses	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	3
Fair value	$ 807
Gross unrealized losses	$ (34)
Number of securities in a continuous loss position | Securities	52
Fixed maturity securities | State and Political Subdivisions
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 1,531	$ 339
Less than 12 months, Gross unrealized losses	$ (193)	$ (6)
Less than 12 months, Number of securities in a continuous loss position | Securities	272	67
12 months or more, Fair value	$ 25	$ 0
12 months or more, Gross unrealized losses	$ (3)	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	5	0
Fair value	$ 1,556	$ 339
Gross unrealized losses	$ (196)	$ (6)
Number of securities in a continuous loss position | Securities	277	67
Fixed maturity securities | Non-U.S. government
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 389	$ 173
Less than 12 months, Gross unrealized losses	$ (73)	$ (9)
Less than 12 months, Number of securities in a continuous loss position | Securities	64	28
12 months or more, Fair value	$ 73	$ 19
12 months or more, Gross unrealized losses	$ (24)	$ (4)
12 months or more, Number of securities in a continuous loss position | Securities	12	1
Fair value	$ 462	$ 192
Gross unrealized losses	$ (97)	$ (13)
Number of securities in a continuous loss position | Securities	76	29
Fixed maturity securities | U.S. corporate
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 17,949	$ 2,593
Less than 12 months, Gross unrealized losses	$ (1,896)	$ (64)
Less than 12 months, Number of securities in a continuous loss position | Securities	2,235	266
12 months or more, Fair value	$ 622	$ 196
12 months or more, Gross unrealized losses	$ (160)	$ (15)
12 months or more, Number of securities in a continuous loss position | Securities	72	22
Fair value	$ 18,571	$ 2,789
Gross unrealized losses	$ (2,056)	$ (79)
Number of securities in a continuous loss position | Securities	2,307	288
Fixed maturity securities | Non-U.S. corporate
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 5,407	$ 912
Less than 12 months, Gross unrealized losses	$ (558)	$ (21)
Less than 12 months, Number of securities in a continuous loss position | Securities	691	124
12 months or more, Fair value	$ 248	$ 62
12 months or more, Gross unrealized losses	$ (66)	$ (5)
12 months or more, Number of securities in a continuous loss position | Securities	35	8
Fair value	$ 5,655	$ 974
Gross unrealized losses	$ (624)	$ (26)
Number of securities in a continuous loss position | Securities	726	132
Fixed maturity securities | Residential mortgage-backed
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 474	$ 97
Less than 12 months, Gross unrealized losses	$ (36)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	121	22
12 months or more, Fair value	$ 4	$ 0
12 months or more, Gross unrealized losses	$ (1)	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	5	0
Fair value	$ 478	$ 97
Gross unrealized losses	$ (37)	$ (1)
Number of securities in a continuous loss position | Securities	126	22
Fixed maturity securities | Commercial mortgage-backed
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 1,882	$ 113
Less than 12 months, Gross unrealized losses	$ (137)	$ (2)
Less than 12 months, Number of securities in a continuous loss position | Securities	265	17
12 months or more, Fair value	$ 42	$ 31
12 months or more, Gross unrealized losses	$ (5)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	6	4
Fair value	$ 1,924	$ 144
Gross unrealized losses	$ (142)	$ (3)
Number of securities in a continuous loss position | Securities	271	21
Fixed maturity securities | Other asset-backed
Schedule of Investments [Line Items]
Less than 12 months, Fair value	$ 1,798	$ 764
Less than 12 months, Gross unrealized losses	$ (113)	$ (7)
Less than 12 months, Number of securities in a continuous loss position | Securities	319	111
12 months or more, Fair value	$ 78	$ 0
12 months or more, Gross unrealized losses	$ (6)	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	19	0
Fair value	$ 1,876	$ 764
Gross unrealized losses	$ (119)	$ (7)
Number of securities in a continuous loss position | Securities	338	111