Shareholders' Equity - Changes in AOCI by Component (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
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			$ 6,839
New accounting pronouncement or change in accounting principle, effect of change on net income					$ (32)
Other comprehensive income (loss) before reclassifications	$ (83)	$ 15	(278)	$ 229
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(7)	7	(14)	54
Net investment income	98	99	298	322
Tax (provision) benefit	(14)	(105)	(46)	(157)
Total amount reclassified from AOCI, net of tax	(9)	4	(16)	52
Net current period other comprehensive income (loss)	(74)	11	(262)	177
Ending balance	6,583		6,583
Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(7)	7	(13)	53
Net investment income				28
Fair value gains (losses) on FG VIEs	(2)		(6)
Total before tax	(9)	7	(19)	81
Tax (provision) benefit	0	(3)	3	(29)
Total Accumulated Other Comprehensive Income [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	152	315	372	149
Amounts reclassified from AOCI to:
Ending balance	78	326	78	326
Net Unrealized Gains (Losses) on Investments with no OTTI [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	83	228	273	171
New accounting pronouncement or change in accounting principle, effect of change on net income					1
Other comprehensive income (loss) before reclassifications	(59)	27	(245)	133
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	15	5	64
Net current period other comprehensive income (loss)	(59)	12	(250)	69
Ending balance	24	240	24	240
Net Unrealized Gains (Losses) on Investments with no OTTI [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	1	24	6	71
Net investment income				28
Fair value gains (losses) on FG VIEs	0		0
Total before tax	1	24	6	99
Tax (provision) benefit	(1)	(9)	(1)	(35)
Net Unrealized Gains (Losses) on Investments with OTTI [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	124	107	120	10
New accounting pronouncement or change in accounting principle, effect of change on net income					0
Other comprehensive income (loss) before reclassifications	(16)	(15)	(21)	81
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	(7)	(11)	(16)	(12)
Net current period other comprehensive income (loss)	(9)	(4)	(5)	93
Ending balance	115	103	115	103
Net Unrealized Gains (Losses) on Investments with OTTI [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(8)	(17)	(19)	(18)
Net investment income				0
Fair value gains (losses) on FG VIEs	0		0
Total before tax	(8)	(17)	(19)	(18)
Tax (provision) benefit	1	6	3	6
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	(31)		0
New accounting pronouncement or change in accounting principle, effect of change on net income					(33)
Other comprehensive income (loss) before reclassifications	(5)		(6)
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	(2)		(5)
Net current period other comprehensive income (loss)	(3)		(1)
Ending balance	(34)		(34)
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	(2)		(6)
Total before tax	(2)		(6)
Tax (provision) benefit	0		1
Cumulative Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(32)	(27)	(29)	(39)
New accounting pronouncement or change in accounting principle, effect of change on net income					0
Other comprehensive income (loss) before reclassifications	(3)	3	(6)	15
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	0	0	0
Net current period other comprehensive income (loss)	(3)	3	(6)	15
Ending balance	(35)	(24)	(35)	(24)
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