Gross Unrealized Losses and Fair Value of Corporate Securities Based on Industries (Detail) $ in Millions	Mar. 31, 2022 USD ($) Securities	Dec. 31, 2021 USD ($) Securities
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 14,957	$ 4,991
Less than 12 months, Gross unrealized losses	$ (895)	$ (110)
Less than 12 months, Number of securities in a continuous loss position | Securities	2,062	635
12 months or more, Fair value	$ 1,114	$ 308
12 months or more, Gross unrealized losses	$ (157)	$ (25)
12 months or more, Number of securities in a continuous loss position | Securities	140	35
Fair value	$ 16,071	$ 5,299
Gross unrealized losses	$ (1,052)	$ (135)
Number of securities in a continuous loss position | Securities	2,202	670
Fixed maturity securities
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 14,957	$ 4,991
Less than 12 months, Gross unrealized losses	$ (895)	$ (110)
Less than 12 months, Number of securities in a continuous loss position | Securities	2,062	635
12 months or more, Fair value	$ 1,114	$ 308
12 months or more, Gross unrealized losses	$ (157)	$ (25)
12 months or more, Number of securities in a continuous loss position | Securities	140	35
Fair value	$ 16,071	$ 5,299
Gross unrealized losses	$ (1,052)	$ (135)
Number of securities in a continuous loss position | Securities	2,202	670
Fixed maturity securities | U.S. corporate
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 8,109	$ 2,593
Less than 12 months, Gross unrealized losses	$ (505)	$ (64)
Less than 12 months, Number of securities in a continuous loss position | Securities	995	266
12 months or more, Fair value	$ 627	$ 196
12 months or more, Gross unrealized losses	$ (91)	$ (15)
12 months or more, Number of securities in a continuous loss position | Securities	65	22
Fair value	$ 8,736	$ 2,789
Gross unrealized losses	$ (596)	$ (79)
Number of securities in a continuous loss position | Securities	1,060	288
Fixed maturity securities | U.S. corporate | Utilities
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 1,089	$ 211
Less than 12 months, Gross unrealized losses	$ (56)	$ (7)
Less than 12 months, Number of securities in a continuous loss position | Securities	142	32
12 months or more, Fair value	$ 59	$ 29
12 months or more, Gross unrealized losses	$ (10)	$ (2)
12 months or more, Number of securities in a continuous loss position | Securities	13	7
Fair value	$ 1,148	$ 240
Gross unrealized losses	$ (66)	$ (9)
Number of securities in a continuous loss position | Securities	155	39
Fixed maturity securities | U.S. corporate | Energy
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 740	$ 166
Less than 12 months, Gross unrealized losses	$ (40)	$ (3)
Less than 12 months, Number of securities in a continuous loss position | Securities	87	18
12 months or more, Fair value	$ 63	$ 25
12 months or more, Gross unrealized losses	$ (8)	$ (7)
12 months or more, Number of securities in a continuous loss position | Securities	7	4
Fair value	$ 803	$ 191
Gross unrealized losses	$ (48)	$ (10)
Number of securities in a continuous loss position | Securities	94	22
Fixed maturity securities | U.S. corporate | Finance and insurance
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 2,529	$ 960
Less than 12 months, Gross unrealized losses	$ (173)	$ (22)
Less than 12 months, Number of securities in a continuous loss position | Securities	293	89
12 months or more, Fair value	$ 203	$ 62
12 months or more, Gross unrealized losses	$ (30)	$ (2)
12 months or more, Number of securities in a continuous loss position | Securities	17	3
Fair value	$ 2,732	$ 1,022
Gross unrealized losses	$ (203)	$ (24)
Number of securities in a continuous loss position | Securities	310	92
Fixed maturity securities | U.S. corporate | Consumer-non-cyclical
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 916	$ 296
Less than 12 months, Gross unrealized losses	$ (56)	$ (7)
Less than 12 months, Number of securities in a continuous loss position | Securities	109	30
12 months or more, Fair value	$ 86	$ 14
12 months or more, Gross unrealized losses	$ (14)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	7	2
Fair value	$ 1,002	$ 310
Gross unrealized losses	$ (70)	$ (8)
Number of securities in a continuous loss position | Securities	116	32
Fixed maturity securities | U.S. corporate | Technology and communications
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 1,094	$ 378
Less than 12 months, Gross unrealized losses	$ (73)	$ (12)
Less than 12 months, Number of securities in a continuous loss position | Securities	147	37
12 months or more, Fair value	$ 93	$ 29
12 months or more, Gross unrealized losses	$ (14)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	8	2
Fair value	$ 1,187	$ 407
Gross unrealized losses	$ (87)	$ (13)
Number of securities in a continuous loss position | Securities	155	39
Fixed maturity securities | U.S. corporate | Industrial
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 361	$ 143
Less than 12 months, Gross unrealized losses	$ (26)	$ (3)
Less than 12 months, Number of securities in a continuous loss position | Securities	46	18
12 months or more, Fair value	$ 0	$ 0
12 months or more, Gross unrealized losses	$ 0	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	0	0
Fair value	$ 361	$ 143
Gross unrealized losses	$ (26)	$ (3)
Number of securities in a continuous loss position | Securities	46	18
Fixed maturity securities | U.S. corporate | Capital goods
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 553	$ 171
Less than 12 months, Gross unrealized losses	$ (35)	$ (3)
Less than 12 months, Number of securities in a continuous loss position | Securities	65	16
12 months or more, Fair value	$ 27	$ 18
12 months or more, Gross unrealized losses	$ (4)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	4	2
Fair value	$ 580	$ 189
Gross unrealized losses	$ (39)	$ (4)
Number of securities in a continuous loss position | Securities	69	18
Fixed maturity securities | U.S. corporate | Consumer-cyclical
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 507	$ 268
Less than 12 months, Gross unrealized losses	$ (34)	$ (7)
Less than 12 months, Number of securities in a continuous loss position | Securities	65	26
12 months or more, Fair value	$ 78	$ 0
12 months or more, Gross unrealized losses	$ (10)	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	7	0
Fair value	$ 585	$ 268
Gross unrealized losses	$ (44)	$ (7)
Number of securities in a continuous loss position | Securities	72	26
Fixed maturity securities | U.S. corporate | Transportation
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 247
Less than 12 months, Gross unrealized losses	$ (9)
Less than 12 months, Number of securities in a continuous loss position | Securities	32
12 months or more, Fair value	$ 0
12 months or more, Gross unrealized losses	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	0
Fair value	$ 247
Gross unrealized losses	$ (9)
Number of securities in a continuous loss position | Securities	32
Fixed maturity securities | U.S. corporate | Other
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 73	$ 0
Less than 12 months, Gross unrealized losses	$ (3)	$ 0
Less than 12 months, Number of securities in a continuous loss position | Securities	9	0
12 months or more, Fair value	$ 18	$ 19
12 months or more, Gross unrealized losses	$ (1)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	2	2
Fair value	$ 91	$ 19
Gross unrealized losses	$ (4)	$ (1)
Number of securities in a continuous loss position | Securities	11	2
Fixed maturity securities | Non-U.S. corporate
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 2,672	$ 912
Less than 12 months, Gross unrealized losses	$ (173)	$ (21)
Less than 12 months, Number of securities in a continuous loss position | Securities	355	124
12 months or more, Fair value	$ 258	$ 62
12 months or more, Gross unrealized losses	$ (39)	$ (5)
12 months or more, Number of securities in a continuous loss position | Securities	31	8
Fair value	$ 2,930	$ 974
Gross unrealized losses	$ (212)	$ (26)
Number of securities in a continuous loss position | Securities	386	132
Fixed maturity securities | Non-U.S. corporate | Utilities
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 272	$ 69
Less than 12 months, Gross unrealized losses	$ (13)	$ (2)
Less than 12 months, Number of securities in a continuous loss position | Securities	28	9
12 months or more, Fair value	$ 12	$ 0
12 months or more, Gross unrealized losses	$ (2)	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	1	0
Fair value	$ 284	$ 69
Gross unrealized losses	$ (15)	$ (2)
Number of securities in a continuous loss position | Securities	29	9
Fixed maturity securities | Non-U.S. corporate | Energy
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 291	$ 64
Less than 12 months, Gross unrealized losses	$ (18)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	27	10
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	1	0
Fair value	$ 295	$ 64
Gross unrealized losses	$ (19)	$ (1)
Number of securities in a continuous loss position | Securities	28	10
Fixed maturity securities | Non-U.S. corporate | Finance and insurance
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 685	$ 366
Less than 12 months, Gross unrealized losses	$ (47)	$ (8)
Less than 12 months, Number of securities in a continuous loss position | Securities	96	43
12 months or more, Fair value	$ 157	$ 18
12 months or more, Gross unrealized losses	$ (23)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	16	2
Fair value	$ 842	$ 384
Gross unrealized losses	$ (70)	$ (9)
Number of securities in a continuous loss position | Securities	112	45
Fixed maturity securities | Non-U.S. corporate | Consumer-non-cyclical
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 253	$ 67
Less than 12 months, Gross unrealized losses	$ (21)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	32	12
12 months or more, Fair value	$ 6	$ 6
12 months or more, Gross unrealized losses	$ (1)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	1	1
Fair value	$ 259	$ 73
Gross unrealized losses	$ (22)	$ (2)
Number of securities in a continuous loss position | Securities	33	13
Fixed maturity securities | Non-U.S. corporate | Technology and communications
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 269	$ 48
Less than 12 months, Gross unrealized losses	$ (17)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	41	8
12 months or more, Fair value	$ 0	$ 0
12 months or more, Gross unrealized losses	$ 0	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	0	0
Fair value	$ 269	$ 48
Gross unrealized losses	$ (17)	$ (1)
Number of securities in a continuous loss position | Securities	41	8
Fixed maturity securities | Non-U.S. corporate | Industrial
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 274	$ 122
Less than 12 months, Gross unrealized losses	$ (19)	$ (3)
Less than 12 months, Number of securities in a continuous loss position | Securities	35	14
12 months or more, Fair value	$ 18	$ 0
12 months or more, Gross unrealized losses	$ (2)	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	2	0
Fair value	$ 292	$ 122
Gross unrealized losses	$ (21)	$ (3)
Number of securities in a continuous loss position | Securities	37	14
Fixed maturity securities | Non-U.S. corporate | Capital goods
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 231	$ 78
Less than 12 months, Gross unrealized losses	$ (16)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	30	8
12 months or more, Fair value	$ 0	$ 0
12 months or more, Gross unrealized losses	$ 0	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	0	0
Fair value	$ 231	$ 78
Gross unrealized losses	$ (16)	$ (1)
Number of securities in a continuous loss position | Securities	30	8
Fixed maturity securities | Non-U.S. corporate | Consumer-cyclical
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 128	$ 22
Less than 12 months, Gross unrealized losses	$ (7)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	25	8
12 months or more, Fair value	$ 20	$ 15
12 months or more, Gross unrealized losses	$ (2)	$ (1)
12 months or more, Number of securities in a continuous loss position | Securities	4	3
Fair value	$ 148	$ 37
Gross unrealized losses	$ (9)	$ (2)
Number of securities in a continuous loss position | Securities	29	11
Fixed maturity securities | Non-U.S. corporate | Transportation
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 125	$ 37
Less than 12 months, Gross unrealized losses	$ (7)	$ (1)
Less than 12 months, Number of securities in a continuous loss position | Securities	19	7
12 months or more, Fair value	$ 0	$ 0
12 months or more, Gross unrealized losses	$ 0	$ 0
12 months or more, Number of securities in a continuous loss position | Securities	0	0
Fair value	$ 125	$ 37
Gross unrealized losses	$ (7)	$ (1)
Number of securities in a continuous loss position | Securities	19	7
Fixed maturity securities | Non-U.S. corporate | Other
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 144	$ 39
Less than 12 months, Gross unrealized losses	$ (8)	$ (2)
Less than 12 months, Number of securities in a continuous loss position | Securities	22	5
12 months or more, Fair value	$ 41	$ 23
12 months or more, Gross unrealized losses	$ (8)	$ (2)
12 months or more, Number of securities in a continuous loss position | Securities	6	2
Fair value	$ 185	$ 62
Gross unrealized losses	$ (16)	$ (4)
Number of securities in a continuous loss position | Securities	28	7
Fixed maturity securities | Corporate Debt Securities
Available for Sale Securities Continuous Unrealized Loss Position [Line Items]
Less than 12 months, Fair value	$ 10,781	$ 3,505
Less than 12 months, Gross unrealized losses	$ (678)	$ (85)
Less than 12 months, Number of securities in a continuous loss position | Securities	1,350	390
12 months or more, Fair value	$ 885	$ 258
12 months or more, Gross unrealized losses	$ (130)	$ (20)
12 months or more, Number of securities in a continuous loss position | Securities	96	30
Fair value	$ 11,666	$ 3,763
Gross unrealized losses	$ (808)	$ (105)
Number of securities in a continuous loss position | Securities	1,446	420