Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			$ 20
Balance, beginning of period	$ 1,837	$ 1,248
OCI before reclassifications	(1,095)	183
Deferred income tax benefit (expense)	233	(80)
AOCI before reclassifications, net of income tax	960	1,351
Amounts reclassified from AOCI	50	80
Deferred income tax benefit (expense)	(11)	(35)
Amounts reclassified from AOCI, net of income tax	39	45
Balance, end of period	999	1,396
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			(15)
Balance, beginning of period	1,709	1,019
OCI before reclassifications	(1,024)	209
Deferred income tax benefit (expense)	218	(90)
AOCI before reclassifications, net of income tax	888	1,138
Amounts reclassified from AOCI	58	90
Deferred income tax benefit (expense)	(12)	(38)
Amounts reclassified from AOCI, net of income tax	46	52
Balance, end of period	934	1,190
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			0
Balance, beginning of period	151	258
OCI before reclassifications	(73)	(19)
Deferred income tax benefit (expense)	15	7
AOCI before reclassifications, net of income tax	93	246
Amounts reclassified from AOCI	(8)	(10)
Deferred income tax benefit (expense)	1	3
Amounts reclassified from AOCI, net of income tax	(7)	(7)
Balance, end of period	86	239
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets			0
Balance, beginning of period	(23)	(29)
OCI before reclassifications	2	(7)
Deferred income tax benefit (expense)	0	3
AOCI before reclassifications, net of income tax	(21)	(33)
Amounts reclassified from AOCI	0	0
Deferred income tax benefit (expense)	0	0
Amounts reclassified from AOCI, net of income tax	0	0
Balance, end of period	(21)	$ (33)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	15		$ (15)
Restatement Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	1,822
Restatement Adjustment [Member] | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	1,694
Restatement Adjustment [Member] | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	151
Restatement Adjustment [Member] | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ (23)