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	$ 64,079	$ 60,920
Gross Unrealized Gains	7,136	3,068
Gross Unrealized Temporary Losses	183	1,383
Gross Unrealized OTTI Losses	(4)	(3)
Estimated Fair Value	71,036	62,608
U.S. corporate
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,375	24,312
Gross Unrealized Gains	2,852	830
Gross Unrealized Temporary Losses	67	669
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	31,160	24,473
Foreign corporate
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,177	8,183
Gross Unrealized Gains	741	159
Gross Unrealized Temporary Losses	74	316
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	9,844	8,026
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,692	8,428
Gross Unrealized Gains	438	246
Gross Unrealized Temporary Losses	16	129
Gross Unrealized OTTI Losses	(4)	(2)
Estimated Fair Value	9,118	8,547
U.S. government and agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,529	7,944
Gross Unrealized Gains	1,869	1,263
Gross Unrealized Temporary Losses	2	112
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	7,396	9,095
CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,500	5,292
Gross Unrealized Gains	264	43
Gross Unrealized Temporary Losses	9	88
Gross Unrealized OTTI Losses	0	(1)
Estimated Fair Value	5,755	5,248
State and political subdivision
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,358	3,200
Gross Unrealized Gains	701	412
Gross Unrealized Temporary Losses	2	15
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	4,057	3,597
ABS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,945	2,135
Gross Unrealized Gains	21	13
Gross Unrealized Temporary Losses	11	22
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	1,955	2,126
Foreign government
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,503	1,426
Gross Unrealized Gains	250	102
Gross Unrealized Temporary Losses	2	32
Gross Unrealized OTTI Losses	0	0
Estimated Fair Value	$ 1,751	$ 1,496

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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