Investments (Fixed Maturity Securities AFS by Sector) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	$ 59,886	$ 59,672
Debt Securities, Available-for-sale	63,590	61,348
Fixed maturity securities
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	59,886	59,672
Gross Unrealized Gain	4,227	3,025
Gross Unrealized Temporary Loss	526	1,352
Gross Unrealized OTTI Loss	(3)	(3)
Debt Securities, Available-for-sale	63,590	61,348
U.S. corporate
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	24,324	23,902
Gross Unrealized Gain	1,355	816
Gross Unrealized Temporary Loss	231	659
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	25,448	24,059
U.S. government and agency
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	6,259	7,503
Gross Unrealized Gain	1,456	1,251
Gross Unrealized Temporary Loss	29	110
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	7,686	8,644
RMBS
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	8,521	8,309
Gross Unrealized Gain	298	246
Gross Unrealized Temporary Loss	62	122
Gross Unrealized OTTI Loss	(3)	(2)
Debt Securities, Available-for-sale	8,760	8,435
Foreign corporate
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	8,732	8,044
Gross Unrealized Gain	319	157
Gross Unrealized Temporary Loss	147	306
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	8,904	7,895
CMBS
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	5,210	5,177
Gross Unrealized Gain	127	42
Gross Unrealized Temporary Loss	33	87
Gross Unrealized OTTI Loss	0	(1)
Debt Securities, Available-for-sale	5,304	5,133
State and political subdivision
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	3,286	3,202
Gross Unrealized Gain	511	399
Gross Unrealized Temporary Loss	3	15
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	3,794	3,586
ABS
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	2,060	2,120
Gross Unrealized Gain	15	13
Gross Unrealized Temporary Loss	12	22
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	2,063	2,111
Foreign government
Debt Securities, Available-for-sale [Abstract]
Amortized cost of fixed maturity securities available-for-sale	1,494	1,415
Gross Unrealized Gain	146	101
Gross Unrealized Temporary Loss	9	31
Gross Unrealized OTTI Loss	0	0
Debt Securities, Available-for-sale	$ 1,631	$ 1,485