Shareholders' Equity - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	$ 239	$ 332	$ 370	$ 160
Other comprehensive income (loss) before reclassifications	22	(9)	(103)	155
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	(27)	(19)	(20)	(25)
Net investment income	112	102	311	301
Interest expense	(25)	(27)	(76)	(67)
Total (provision) benefit for income taxes	(43)	(133)	(220)	(219)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	12	10	7	19
Net current period other comprehensive income (loss)	34	1	(97)	173
Balance at end of period	273	333	273	333
Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	27	15	20	28
Net investment income	(9)		(9)
Interest expense	0	0	(1)	0
Total before tax	18	15	10	28
Total (provision) benefit for income taxes	(6)	(5)	(4)	(10)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	12	10	6	18
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	236	345	367	178
Other comprehensive income (loss) before reclassifications	41	(5)	(77)	164
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	42	(8)	(89)	159
Balance at end of period	278	337	278	337
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)	10	(5)	(9)	(9)
Net investment income	(9)		(9)
Interest expense	0	0	0	0
Total before tax	1	(5)	(18)	(9)
Total (provision) benefit for income taxes	0	2	6	4
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	1	(3)	(12)	(5)
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	(22)	4	(24)
Other comprehensive income (loss) before reclassifications	(15)	1	(23)	(8)
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	(4)	14	(4)	16
Balance at end of period	0	(8)	0	(8)
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	20	29	37
Net investment income	0		0
Interest expense	0	0	0	0
Total before tax	17	20	29	37
Total (provision) benefit for income taxes	(6)	(7)	(10)	(13)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	11	13	19	24
Accumulated Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(9)	1	(10)	(3)
Other comprehensive income (loss) before reclassifications	(4)	(5)	(3)	(1)
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	(4)	(5)	(3)	(1)
Balance at end of period	(13)	(4)	(13)	(4)
Accumulated 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		0
Interest expense	0	0	0	0
Total before tax	0	0	0	0
Total (provision) benefit for income taxes	0	0	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	0	0
Cash Flow Hedge [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	8	8	9	9
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)	0	0	(1)	(1)
Balance at end of period	8	8	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	0	0
Net investment income	0		0
Interest expense	0		(1)	0
Total before tax	0	0	(1)	0
Total (provision) benefit for income taxes	0	0	0	(1)
Less: reclassification adjustment for gains (losses) included in net income (loss), net of tax provision (benefit) of $(21), $5 and $(7)	$ 0	$ 0	$ (1)	$ (1)