Investments (Changes in Net Unrealized Investment Gains Losses) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Income Loss Attributable To Company	$ 833	$ 1,860
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		(4)
Balance, December 31, 2017	833	1,860
Fixed maturity securities on which noncredit OTTI losses have been recognized	4
Unrealized investment gains (losses) during the period	(2,453)
Unrealized investment gains (losses) relating to:
Future policy benefits	1,131
Changes In Net Unrealized Investment Gains Losses Related To Dac And Voba Related To Non Credit Otti Losses Recognized In Other Comprehensive Income Loss	(3)
DAC, VOBA and DSI	101
Changes In Net Unrealized Investment Gains (Losses) Related To Deferred Income Tax Benefit (Expense) Related To Non Credit Otti Losses Recognized In Other Comprehensive Income (Loss)	1
Deferred income tax benefit (expense)	271
Balance, June 30, 2018	833
Change in net unrealized investment gains (losses)	$ (948)
AOCI Attributable to Parent [Member]
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets		(79)
Restatement Adjustment [Member]
Changes In Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Loss [Abstract]
Net Unrealized Investment Gains Losses Included In Accumulated Other Comprehensive Income Loss Attributable To Company		1,781
Balance, December 31, 2017		$ 1,781