Accumulated Other Comprehensive Income Loss - AOCI Rollforward (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 13,494			$ 13,494
OCI, net of tax		$ (166)	$ 91	(2,177)	$ 922
Ending balance		12,729	17,233	12,729	17,233
TaxCutsAndJobsActOf2017ReclassificationFromAociToRetainedEarningsTaxEffect	(88)
Equity securities and shadow DAC [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting changes, net of tax [1]	93
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent		(183)	119	(2,213)	683
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,931	211	1,755	1,931	1,276
Cumulative effect of accounting changes, net of tax [1]						$ 273
Adjusted balance, beginning of period						2,204
Amounts reclassified from AOCI		12	(34)	49	(119)
OCI, net of tax		(171)	85	(2,164)	564
Ending balance		40	1,840	40	1,840
Accumulated Other-than-Temporary Impairment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent		(1)	(1)	0	(1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(3)	(3)	(3)	(3)	(3)
Cumulative effect of accounting changes, net of tax [1]						0
Adjusted balance, beginning of period						(3)
Amounts reclassified from AOCI		0	0	(1)	0
OCI, net of tax		(1)	(1)	(1)	(1)
Ending balance		(4)	(4)	(4)	(4)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent		1	(2)	(12)	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	18	(12)	57	18	76
Cumulative effect of accounting changes, net of tax [1]						2
Adjusted balance, beginning of period						20
Amounts reclassified from AOCI		(6)	(12)	(25)	(40)
OCI, net of tax		(5)	(14)	(37)	(33)
Ending balance		(17)	43	(17)	43
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent		1	14	(4)	21
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	34	33	13	34	6
Cumulative effect of accounting changes, net of tax [1]						4
Adjusted balance, beginning of period						38
Amounts reclassified from AOCI		0	0	0	0
OCI, net of tax		1	14	(4)	21
Ending balance		34	27	34	27
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent		1	1	0	(144)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(1,317)	(1,582)	(1,328)	(1,317)	(1,692)
Cumulative effect of accounting changes, net of tax [1]						(284)
Adjusted balance, beginning of period						(1,601)
Amounts reclassified from AOCI		9	6	29	515
OCI, net of tax		10	7	29	371
Ending balance		(1,572)	(1,321)	(1,572)	(1,321)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
OCI, before Reclassifications, Net of Tax, Attributable to Parent		(181)	131	(2,229)	566
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 663	(1,353)	494	663	(337)
Cumulative effect of accounting changes, net of tax [1]						(5)	$ 0
Adjusted balance, beginning of period						$ 658	$ (337)
Amounts reclassified from AOCI		15	(40)	52	356
OCI, net of tax		(166)	91	(2,177)	922
Ending balance		$ (1,519)	$ 585	$ (1,519)	$ 585