Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
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)	$ (79)
Balance beginning of period	1,837	1,248	$ 1,594
OCI before reclassifications	(1,382)	386	(498)
Deferred income tax benefit (expense)	382	(155)	160
AOCI before reclassifications, net of income tax	758	1,479	1,256
Amounts reclassified from AOCI	45	47	(13)
Deferred income tax benefit (expense)	(85)	311	5
Amounts reclassified from AOCI, net of income tax	(40)	358	(8)
Balance end of period	718	1,837	1,248
Adjustments for New Accounting Pronouncement [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
Accumulated Net Investment Gain (Loss) 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		(79)
Balance beginning of period	1,709	1,019	1,379
OCI before reclassifications	(1,534)	529	(565)
Deferred income tax benefit (expense)	327	(206)	185
AOCI before reclassifications, net of income tax	423	1,342	999
Amounts reclassified from AOCI	179	61	30
Deferred income tax benefit (expense)	(38)	306	(10)
Amounts reclassified from AOCI, net of income tax	141	367	20
Balance end of period	564	1,709	1,019
Accumulated Net Gain (Loss) from Cash Flow Hedges 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		0
Balance beginning of period	151	258	241
OCI before reclassifications	156	(152)	70
Deferred income tax benefit (expense)	54	54	(25)
AOCI before reclassifications, net of income tax	361	160	286
Amounts reclassified from AOCI	(134)	(14)	(43)
Deferred income tax benefit (expense)	(47)	5	15
Amounts reclassified from AOCI, net of income tax	(181)	(9)	(28)
Balance end of period	180	151	258
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Adjustments for New Accounting Pronouncement [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		330
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)	(26)
OCI before reclassifications	(4)	9	(3)
Deferred income tax benefit (expense)	1	(3)	0
AOCI before reclassifications, net of income tax	(26)	(23)	(29)
Amounts reclassified from AOCI	0	0	0
Deferred income tax benefit (expense)	0	0	0
Amounts reclassified from AOCI, net of income tax	0	0	0
Balance end of period	(26)	(23)	$ (29)
Restatement Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	1,758
Balance end of period		1,758
Restatement Adjustment [Member] | Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	1,630
Balance end of period		1,630
Restatement Adjustment [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	151
Balance end of period		151
Restatement Adjustment [Member] | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance beginning of period	$ (23)
Balance end of period		$ (23)