Accumulated Other Comprehensive Income Loss Level 4 (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (207)	$ 254	$ (337)	$ (329)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	157	617
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(27)	(34)
Other Comprehensive Income (Loss), Net of Tax	130	583
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Gain (Loss) on Investments, Excluding Other than Temporary Impairments	(19)	(132)
Income Tax Expense (Benefit)	109	58
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	27	34
Gain (Loss) on Investments [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	4
Gain (Loss) on Investments [Member] | Currency Swap [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1
Investment Income [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	16
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,413	1,801	1,276	1,279
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	160	549
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(23)	(27)
Other Comprehensive Income (Loss), Net of Tax	137	522
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	23	27
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Gain (Loss) on Investments, Excluding Other than Temporary Impairments	36	41
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	36	41
Income Tax Expense (Benefit)	13	14
Accumulated Other-than-Temporary Impairment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(4)	(15)	(3)	(7)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1)	(9)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	1
Other Comprehensive Income (Loss), Net of Tax	(1)	(8)
Accumulated Other-than-Temporary Impairment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		(1)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Gain (Loss) on Investments, Excluding Other than Temporary Impairments		(1)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		(1)
Income Tax Expense (Benefit)		0
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	58	184	76	130
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(4)	70
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(14)	(16)
Other Comprehensive Income (Loss), Net of Tax	(18)	54
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	14	16
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	21	24
Income Tax Expense (Benefit)	7	8
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	8	(49)	6	(55)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	2	6
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Net of Tax	2	6
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(1,682)	(1,667)	$ (1,692)	$ (1,676)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	1
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	10	8
Other Comprehensive Income (Loss), Net of Tax	10	9
Accumulated Defined Benefit Plans Adjustment [Member] | Other Postretirement Benefit Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(10)	(8)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	1	2
Defined Benefit Plan, Actuarial Gain (Loss)	(16)	(15)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(15)	(13)
Income Tax Expense (Benefit)	(5)	(5)
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	21	$ 24
Designated as Hedging Instrument [Member] | Gain (Loss) on Investments [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	4
Designated as Hedging Instrument [Member] | Gain (Loss) on Investments [Member] | Currency Swap [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1
Designated as Hedging Instrument [Member] | Investment Income [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 16