Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 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					$ (4)
Balance, beginning of period			$ 1,837
Balance, end of period	$ 560		560
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					(79)
Balance, beginning of period	671	$ 1,675	1,709	$ 1,019
OCI before reclassifications	(298)	(852)	(1,633)	106
Other Comprehensive Income (Loss) before Reclassifications, Tax	61	305	361	(52)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	434	1,128	358	1,073
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	37	(23)	136	65
Balance, end of period	463	1,107	463	1,107
Reclassification from AOCI, Current Period, Tax	(8)	2	(31)	(31)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	29	(21)	105	34
Accumulated Gain (Loss), Net, Cash Flow Hedge, 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					0
Balance, beginning of period	162	217	151	258
OCI before reclassifications	(7)	(50)	28	(101)
Other Comprehensive Income (Loss) before Reclassifications, Tax	2	17	(6)	35
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	157	184	173	192
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(46)	(1)	(65)	(13)
Balance, end of period	122	184	122	184
Reclassification from AOCI, Current Period, Tax	11	1	14	5
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(35)	0	(51)	(8)
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	(18)	(31)	(23)	(29)
OCI before reclassifications	(8)	9	(2)	4
Other Comprehensive Income (Loss) before Reclassifications, Tax	1	(4)	0	(1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(25)	(26)	(25)	(26)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	0	0	0
Balance, end of period	(25)	(26)	(25)	(26)
Reclassification from AOCI, Current Period, Tax	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0	0
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets					$ (79)
Balance, beginning of period	815	1,861	1,837	1,248
OCI before reclassifications	(313)	(893)	(1,607)	9
Other Comprehensive Income (Loss) before Reclassifications, Tax	64	318	355	(18)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	566	1,286	506	1,239
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	(9)	(24)	71	52
Balance, end of period	560	1,265	560	1,265
Reclassification from AOCI, Current Period, Tax	3	3	(17)	(26)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (6)	$ (21)	54	$ 26
Restatement Adjustment | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period			1,630
Restatement Adjustment | Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period			151
Restatement Adjustment | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period			(23)
Restatement Adjustment | AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period			$ 1,758