Shareholders' Equity - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	$ 237	$ 370
Other comprehensive income (loss) before reclassifications	76	11
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(13)	16
Net investment income	99	101
Interest expense	(26)	(25)
Total (provision) benefit for income taxes	(6)	(65)
Total amount reclassified from AOCI, net of tax	6	(10)
Net current period other comprehensive income (loss)	82	0
Balance at end of period	319	370
Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	13	(16)
Net investment income	(3)
Interest expense	0	(1)
Total before tax	10	(17)
Total (provision) benefit for income taxes	(4)	6
Total amount reclassified from AOCI, net of tax	6	(11)
Net Unrealized Gains (Losses) on Investments with no Other-Than-Temporary Impairment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	260	367
Other comprehensive income (loss) before reclassifications	95	18
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	90	5
Balance at end of period	350	372
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)	(4)	(20)
Net investment income	(3)
Interest expense	0	0
Total before tax	(7)	(20)
Total (provision) benefit for income taxes	2	7
Total amount reclassified from AOCI, net of tax	(5)	(13)
Net Unrealized Gains (Losses) on Investments with Other-Than-Temporary Impairment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(15)	4
Other comprehensive income (loss) before reclassifications	(17)	(2)
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	(6)	1
Balance at end of period	(21)	5
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)	17	4
Net investment income	0
Interest expense	0	0
Total before tax	17	4
Total (provision) benefit for income taxes	(6)	(1)
Total amount reclassified from AOCI, net of tax	11	3
Accumulated Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(16)	(10)
Other comprehensive income (loss) before reclassifications	(2)	(5)
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	(2)	(5)
Balance at end of period	(18)	(15)
Accumulated 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
Interest expense	0	0
Total before tax	0	0
Total (provision) benefit for income taxes	0	0
Total amount reclassified from AOCI, net of tax	0	0
Cash Flow Hedge [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	8	9
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	0	(1)
Balance at end of period	8	8
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
Interest expense	0	(1)
Total before tax	0	(1)
Total (provision) benefit for income taxes	0	0
Total amount reclassified from AOCI, net of tax	$ 0	$ (1)