Shareholders' Equity - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 6,839
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(5)	$ 32
Net investment income	101	122
Interest expense	(24)	(24)
Tax (provision) benefit	(20)	(55)
Ending balance	6,784
Net Unrealized Gains (Losses) on Investments with no Other-Than-Temporary Impairment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income	1
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	273	171
Other comprehensive income (loss) before reclassifications	(122)	44
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	(6)	(45)
Net current period other comprehensive income (loss)	(128)	(1)
Ending balance	146	170
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)	(6)	(41)
Net investment income	0	(28)
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0
Interest expense	0	0
Total before tax	(6)	(69)
Tax (provision) benefit	0	24
Net Unrealized Gains (Losses) on Investments with Other-Than-Temporary Impairment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income	0
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	120	10
Other comprehensive income (loss) before reclassifications	(11)	50
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	9	6
Net current period other comprehensive income (loss)	(2)	56
Ending balance	118	66
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)	11	9
Net investment income	0	0
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0
Interest expense	0	0
Total before tax	11	9
Tax (provision) benefit	(2)	(3)
Net Unrealized Gains (Losses) on FG VIE Liabilities with Recourse due to Instrument Specific Credit Risk
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income	(33)
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	0
Other comprehensive income (loss) before reclassifications	(4)
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	2
Net current period other comprehensive income (loss)	(2)
Ending balance	(35)
Net Unrealized Gains (Losses) on FG VIE Liabilities with Recourse due to Instrument Specific Credit Risk | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0
Net investment income	0
Fair Value, Option, Changes in Fair Value, Gain (Loss)	3
Interest expense	0
Total before tax	3
Tax (provision) benefit	(1)
Cumulative Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income	0
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(29)	(39)
Other comprehensive income (loss) before reclassifications	6	2
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	0
Net current period other comprehensive income (loss)	6	2
Ending balance	(23)	(37)
Cumulative Translation Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0	0
Net investment income	0	0
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0
Interest expense	0	0
Total before tax	0	0
Tax (provision) benefit	0	0
Cash Flow Hedge [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income	0
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	8	7
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	0	0
Net current period other comprehensive income (loss)	0	0
Ending balance	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
Net investment income	0	0
Fair Value, Option, Changes in Fair Value, Gain (Loss)	0
Interest expense	0	0
Total before tax	0	0
Tax (provision) benefit	0	0
Total Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
New accounting pronouncement or change in accounting principle, effect of change on net income	(32)
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	372	149
Other comprehensive income (loss) before reclassifications	(131)	96
Amounts reclassified from AOCI to:
Total amount reclassified from AOCI, net of tax	5	(39)
Net current period other comprehensive income (loss)	(126)	57
Ending balance	214	206
Total Accumulated Other Comprehensive Income [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	5	(32)
Net investment income	0	(28)
Fair Value, Option, Changes in Fair Value, Gain (Loss)	3
Interest expense	0	0
Total before tax	8	(60)
Tax (provision) benefit	$ (3)	$ 21