Shareholders' Equity - Changes in AOCI by Component (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	$ 370	$ 160
Other comprehensive income (loss) before reclassifications	11	103
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	16	2
Interest expense	(25)	(20)
Total (provision) benefit for income taxes	(65)	(27)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	(10)	2
Net current period other comprehensive income (loss)	0	104
Balance at end of period	370	264
Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(16)	3
Interest expense	(1)	0
Total before tax	(17)	3
Total (provision) benefit for income taxes	6	(2)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	(11)	1
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	367	178
Other comprehensive income (loss) before reclassifications	18	94
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	5	93
Balance at end of period	372	271
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)	(20)	(2)
Interest expense	0	0
Total before tax	(20)	(2)
Total (provision) benefit for income taxes	7	1
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	(13)	(1)
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	4	(24)
Other comprehensive income (loss) before reclassifications	(2)	8
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	1	11
Balance at end of period	5	(13)
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)	4	5
Interest expense	0	0
Total before tax	4	5
Total (provision) benefit for income taxes	(1)	(2)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	3	3
Accumulated Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(10)	(3)
Other comprehensive income (loss) before reclassifications	(5)	1
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	(5)	1
Balance at end of period	(15)	(2)
Accumulated Translation Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	0	0
Interest expense	0	0
Total before tax	0	0
Total (provision) benefit for income taxes	0	0
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	0	0
Cash Flow Hedge [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	9	9
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	(1)	(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
Interest expense	(1)	0
Total before tax	(1)	0
Total (provision) benefit for income taxes	0	(1)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	$ (1)	$ (1)