Investments - Unrealized Capital Losses (Details) $ in Millions	Sep. 30, 2022 USD ($) securities	Dec. 31, 2021 USD ($) securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	3,596	989
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 2,916	$ 111
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 2,330	$ 72
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	4,320	1,326
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	724	337
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,944	$ 708
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	17,309	3,838
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	586	39
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 19,253	$ 4,546
U.S. Treasuries
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	21	4
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 28	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 28	$ 0
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	23	6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	2	2
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 6	$ 7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	253	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 259	$ 14
State, municipalities and political subdivisions
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	295	21
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 90	$ 1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 89	$ 1
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	299	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	4	0
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 2	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	582	33
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 584	$ 33
U.S. corporate public securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	1,068	290
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 1,198	$ 39
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 862	$ 32
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	1,351	428
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	283	138
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 712	$ 110
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	4,922	1,237
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	336	7
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 5,634	$ 1,347
U.S. corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	331	35
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 381	$ 15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 343	$ 2
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	349	43
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	18	8
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 205	$ 94
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	2,918	325
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	38	13
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 3,123	$ 419
Foreign corporate public securities and foreign governments
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	406	90
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 376	$ 14
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 288	$ 13
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	477	107
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	71	17
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 192	$ 21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	1,684	425
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	88	1
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,876	$ 446
Foreign corporate private securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	218	7
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 250	$ 1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 248	$ 1
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	221	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	3	1
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 12	$ 10
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	2,289	54
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,301	$ 64
Residential mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	435	181
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 153	$ 20
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 100	$ 11
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	612	277
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	177	96
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 316	$ 241
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	1,267	400
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	53	9
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,583	$ 641
Commercial mortgage-backed
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	471	178
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 310	$ 15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 260	$ 8
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	555	205
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	84	27
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 358	$ 155
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	2,255	780
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	50	7
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 2,613	$ 935
Other asset-backed securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	349	183
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 127	$ 6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 109	$ 4
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	431	231
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	82	48
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 141	$ 70
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	1,122	577
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	18	2
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 1,263	$ 647
US Government Corporations and Agencies Securities
Available-for-sale Securities Including Securities Pledged [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | securities	2
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 3
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | securities	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | securities	0
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	17
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	$ 17