Investment Holding Level 4 Available-for-Sale Securities (Details) $ in Millions	Sep. 30, 2017 USD ($) securities	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 54,478	$ 53,805
Available-for-sale Equity Securities, Amortized Cost Basis	1,010	1,020
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	3,368	2,704
Available-for-sale Equity Securities, Accumulated Gross Unrealized Gain, before Tax	130	96
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(177)	(506)
Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax	(28)	(19)
Available-for-sale Securities, Debt Securities	57,669	56,003
Available-for-sale Securities, Equity Securities	1,112	1,097
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	(6)	(6)
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	2,289	1,896
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis	8,896	9,015
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis	8,975	9,038
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	20,537	19,962
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	13,781	13,894
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	2,305	1,912
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	9,168	9,289
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	9,352	9,245
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	22,819	21,556
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	14,025	14,001
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	8,695	14,274
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	8,594	13,868
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(101)	(406)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	2,444	2,565
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,340	2,446
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(104)	(119)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	11,139	16,839
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10,934	16,314
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ (205)	(525)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | securities	2,491
Percentage of Gross Unrealized Losses Depressed Less than Twenty Percent of Cost or Amortized Cost	92.00%
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	$ 2,300	2,396
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	20	17
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(15)	(31)
Available-for-sale Securities, Debt Securities	2,305	2,382
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	523	582
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	522	579
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1)	(3)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	230	368
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	216	340
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(14)	(28)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	753	950
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	738	919
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(15)	(31)
Collateralized Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	2,364	1,853
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	33	67
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(2)	(4)
Available-for-sale Securities, Debt Securities	2,395	1,916
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	1,138	641
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,136	640
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2)	(1)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	145	370
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	145	367
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	(3)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	1,283	1,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,281	1,007
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(2)	(4)
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	5,034	4,907
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	123	97
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(37)	(68)
Available-for-sale Securities, Debt Securities	5,120	4,936
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	(6)	(6)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	1,490	2,076
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,472	2,027
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(18)	(49)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	288	293
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	269	274
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(19)	(19)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	1,778	2,369
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,741	2,301
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(37)	(68)
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	23,925	24,380
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	1,901	1,510
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(80)	(224)
Available-for-sale Securities, Debt Securities	25,746	25,666
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	2,317	5,418
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2,289	5,248
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(28)	(170)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	1,447	835
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,395	781
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(52)	(54)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	3,764	6,253
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,684	6,029
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(80)	(224)
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	1,300	1,164
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	71	33
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(6)	(26)
Available-for-sale Securities, Debt Securities	1,365	1,171
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	170	573
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	167	550
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3)	(23)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	59	27
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	56	24
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(3)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	229	600
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	223	574
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(6)	(26)
Municipal Bonds [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	783	1,567
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	774	1,498
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(9)	(69)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	156	43
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	146	41
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(10)	(2)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	939	1,610
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	920	1,539
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(19)	(71)
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	11,585	10,825
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	869	732
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(19)	(71)
Available-for-sale Securities, Debt Securities	12,435	11,486
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	4,083	4,738
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	127	66
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(5)	(37)
Available-for-sale Securities, Debt Securities	4,205	4,767
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	363	1,655
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	359	1,624
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(4)	(31)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	60	591
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	59	585
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(1)	(6)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	423	2,246
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	418	2,209
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(5)	(37)
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	3,887	3,542
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	224	182
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	(13)	(45)
Available-for-sale Securities, Debt Securities	4,098	3,679
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	1,716	1,432
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,705	1,387
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(11)	(45)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	30	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	28	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(2)	0
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	1,746	1,432
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,733	1,387
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(13)	(45)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	40,697	39,911
Available-for-sale Securities, Debt Securities	43,644	42,002
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	8,500	13,944
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	8,424	13,553
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(76)	(391)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	2,415	2,527
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,314	2,412
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(101)	(115)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	10,915	16,471
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10,738	15,965
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(177)	(506)
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Amortized Cost	195	330
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	170	315
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(25)	(15)
Available-for-sale Securities Continuous Unrealized Loss Position Twelve Months or Longer Amortized Cost	29	38
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	26	34
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	(3)	(4)
Available-for-sale Securities Continuous Unrealized Loss Position Amortized Cost	224	368
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	196	349
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	(28)	(19)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	0	0
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Equity Securities, Amortized Cost Basis	1,010	1,020
Available-for-sale Securities, Amortized Cost Basis	55,488	54,825
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,498	2,800
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(205)	(525)
Available-for-sale Securities, Equity Securities	1,112	1,097
Available-for-sale Securities	58,781	57,100
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities	$ (6)	$ (6)