Investments (Fixed Maturity Securities AFS by Sector) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 63,083	$ 59,672
Gross Unrealized Gains	7,060	3,025
Gross Unrealized Temporary Losses	170	1,352
Gross Unrealized OTTI Losses	(4)	(3)
Estimated Fair Value	69,977	61,348
U.S. corporate
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27,841	23,902
Gross Unrealized Gains	2,815	816
Gross Unrealized Temporary Losses	65	659
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	30,591	24,059
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,017	8,044
Gross Unrealized Gains	736	157
Gross Unrealized Temporary Losses	67	306
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	9,686	7,895
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,600	8,309
Gross Unrealized Gains	440	246
Gross Unrealized Temporary Losses	14	122
Gross Unrealized OTTI Losses	(4)	(2)
Estimated Fair Value	9,030	8,435
U.S. government and agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,396	7,503
Gross Unrealized Gains	1,848	1,251
Gross Unrealized Temporary Losses	0	110
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	7,244	8,644
CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,460	5,177
Gross Unrealized Gains	263	42
Gross Unrealized Temporary Losses	9	87
Gross Unrealized OTTI Losses	0	(1)
Estimated Fair Value	5,714	5,133
State and political subdivision
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,326	3,202
Gross Unrealized Gains	687	399
Gross Unrealized Temporary Losses	2	15
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	4,011	3,586
ABS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,940	2,120
Gross Unrealized Gains	21	13
Gross Unrealized Temporary Losses	11	22
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	1,950	2,111
Foreign government
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,503	1,415
Gross Unrealized Gains	250	101
Gross Unrealized Temporary Losses	2	31
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	$ 1,751	$ 1,485

Other-than-temporary impairments on fixed maturity securities transferred to other comprehensive income loss.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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