Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	$ 52,383	$ 25,154
Less than Twelve Months, Unrealized Losses	1,650	1,015
Twelve Months or More, Fair Value	165,273	173,006
Twelve Months or More, Unrealized Losses	34,164	26,855
Fair Value	217,656	198,160
Gross Unrealized Losses	35,814	27,870
U.S. Treasury securities and obligations of U.S. government authorities and agencies
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	4,126	2,718
Less than Twelve Months, Unrealized Losses	114	95
Twelve Months or More, Fair Value	12,469	12,642
Twelve Months or More, Unrealized Losses	4,891	4,074
Fair Value	16,595	15,360
Gross Unrealized Losses	5,005	4,169
Obligations of U.S. states and their political subdivisions
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	1,702	862
Less than Twelve Months, Unrealized Losses	42	14
Twelve Months or More, Fair Value	4,134	3,816
Twelve Months or More, Unrealized Losses	617	445
Fair Value	5,836	4,678
Gross Unrealized Losses	659	459
Foreign government bonds
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	6,945	9,098
Less than Twelve Months, Unrealized Losses	393	542
Twelve Months or More, Fair Value	20,624	19,589
Twelve Months or More, Unrealized Losses	7,117	4,664
Fair Value	27,569	28,687
Gross Unrealized Losses	7,510	5,206
U.S. public corporate securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	21,323	4,881
Less than Twelve Months, Unrealized Losses	670	103
Twelve Months or More, Fair Value	58,506	61,204
Twelve Months or More, Unrealized Losses	11,882	9,604
Fair Value	79,829	66,085
Gross Unrealized Losses	12,552	9,707
U.S. private corporate securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	5,425	3,026
Less than Twelve Months, Unrealized Losses	160	69
Twelve Months or More, Fair Value	27,564	27,062
Twelve Months or More, Unrealized Losses	3,082	2,504
Fair Value	32,989	30,088
Gross Unrealized Losses	3,242	2,573
Foreign public corporate securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	4,580	1,766
Less than Twelve Months, Unrealized Losses	100	37
Twelve Months or More, Fair Value	10,169	10,812
Twelve Months or More, Unrealized Losses	1,469	1,246
Fair Value	14,749	12,578
Gross Unrealized Losses	1,569	1,283
Foreign private corporate securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	5,270	1,578
Less than Twelve Months, Unrealized Losses	156	120
Twelve Months or More, Fair Value	21,281	22,145
Twelve Months or More, Unrealized Losses	4,133	3,324
Fair Value	26,551	23,723
Gross Unrealized Losses	4,289	3,444
Asset-backed securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	1,842	846
Less than Twelve Months, Unrealized Losses	6	30
Twelve Months or More, Fair Value	1,785	5,886
Twelve Months or More, Unrealized Losses	70	89
Fair Value	3,627	6,732
Gross Unrealized Losses	76	119
Commercial mortgage-backed securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	970	287
Less than Twelve Months, Unrealized Losses	6	3
Twelve Months or More, Fair Value	7,228	8,251
Twelve Months or More, Unrealized Losses	676	710
Fair Value	8,198	8,538
Gross Unrealized Losses	682	713
Residential mortgage-backed securities
Debt Securities [Line Items]
Less than Twelve Months, Fair Value	200	92
Less than Twelve Months, Unrealized Losses	3	2
Twelve Months or More, Fair Value	1,513	1,599
Twelve Months or More, Unrealized Losses	227	195
Fair Value	1,713	1,691
Gross Unrealized Losses	$ 230	$ 197