Shareholders' Equity - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			$ 6,839
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	$ (2)	$ 15	(7)	$ 47
Net investment income	99	101	200	223
Interest expense	(24)	(25)	(48)	(49)
Tax (provision) benefit	(12)	3	(32)	(52)
Ending balance	6,634		6,634
Net Unrealized Gains (Losses) on Investments with no Other-Than-Temporary Impairment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	146	170	273	171
New accounting pronouncement or change in accounting principle, effect of change on net income					$ 1
Other comprehensive income (loss) before reclassifications	(64)	62	(186)	106
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	1	(4)	(5)	(49)
Net current period other comprehensive income (loss)	(63)	58	(191)	57
Ending balance	83	228	83	228
Net Unrealized Gains (Losses) on Investments with no Other-Than-Temporary Impairment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	1	(6)	(5)	(47)
Net investment income				(28)
Fair value gains (losses) on FG VIEs	0		0
Total before tax	1	(6)	(5)	(75)
Tax (provision) benefit	0	2	0	26
Net Unrealized Gains (Losses) on Investments with Other-Than-Temporary Impairment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	118	66	120	10
New accounting pronouncement or change in accounting principle, effect of change on net income					0
Other comprehensive income (loss) before reclassifications	6	46	(5)	96
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	(5)	9	1
Net current period other comprehensive income (loss)	6	41	4	97
Ending balance	124	107	124	107
Net Unrealized Gains (Losses) on Investments with Other-Than-Temporary Impairment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0	(8)	11	1
Net investment income				0
Fair value gains (losses) on FG VIEs	0		0
Total before tax	0	(8)	11	1
Tax (provision) benefit	0	3	(2)	0
Net Unrealized Gains (Losses) on FG VIE Liabilities with Recourse due to Instrument Specific Credit Risk [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(35)		0
New accounting pronouncement or change in accounting principle, effect of change on net income					(33)
Other comprehensive income (loss) before reclassifications	3		(1)
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	1		3
Net current period other comprehensive income (loss)	4		2
Ending balance	(31)		(31)
Net Unrealized Gains (Losses) on FG VIE Liabilities with Recourse due to Instrument Specific Credit Risk [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0		0
Fair value gains (losses) on FG VIEs	1		4
Total before tax	1		4
Tax (provision) benefit	0		(1)
Cumulative Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(23)	(37)	(29)	(39)
New accounting pronouncement or change in accounting principle, effect of change on net income					0
Other comprehensive income (loss) before reclassifications	(9)	10	(3)	12
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	0	0	0
Net current period other comprehensive income (loss)	(9)	10	(3)	12
Ending balance	(32)	(27)	(32)	(27)
Cumulative Translation Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0	0	0	0
Net investment income				0
Fair value gains (losses) on FG VIEs	0		0
Total before tax	0	0	0	0
Tax (provision) benefit	0	0	0	0
Cash Flow Hedge [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	8	7	8	7
New accounting pronouncement or change in accounting principle, effect of change on net income					0
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	0	0	0
Net current period other comprehensive income (loss)	0	0	0	0
Ending balance	8	7	8	7
Cash Flow Hedge [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0	0	0	0
Net investment income				0
Fair value gains (losses) on FG VIEs	0		0
Total before tax	0	0	0	0
Tax (provision) benefit	0	0	0	0
Total Accumulated Other Comprehensive Income [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	214	206	372	149
New accounting pronouncement or change in accounting principle, effect of change on net income					$ (32)
Other comprehensive income (loss) before reclassifications	(64)	118	(195)	214
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	2	(9)	7	(48)
Net current period other comprehensive income (loss)	(62)	109	(188)	166
Ending balance	152	315	152	315
Total Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	1	(14)	6	(46)
Net investment income				(28)
Fair value gains (losses) on FG VIEs	1		4
Total before tax	2	(14)	10	(74)
Tax (provision) benefit	$ 0	$ 5	$ (3)	$ 26