Other Comprehensive Income - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period				$ 370				$ 160	$ 370	$ 160	$ 515
Other comprehensive income (loss) before reclassifications									(142)	169	(341)
Amounts reclassified from AOCI to:
Net realized investment gains (losses)	$ (6)	$ (27)	$ (9)	16	$ (35)	$ (19)	$ (8)	2	(26)	(60)	52
Net investment income	112	112	98	101	102	102	96	103	423	403	393
Interest expense	(25)	(25)	(26)	(25)	(25)	(27)	(20)	(20)	(101)	(92)	(82)
Total (provision) benefit for income taxes	(155)	$ (43)	$ (112)	(65)	(224)	$ (133)	$ (59)	(27)	(375)	(443)	(334)
Total amount reclassified from AOCI, net of tax									10	41	(14)
Net current period other comprehensive income (loss)									(133)	210	(355)
Balance at end of period	237				370				237	370	160
Reclassification out of Accumulated Other Comprehensive Income [Member]
Amounts reclassified from AOCI to:
Net realized investment gains (losses)									26	62	(19)
Net investment income									(9)
Interest expense									(1)	0	(1)
Total before tax									16	62	(20)
Total (provision) benefit for income taxes									(7)	(21)	6
Total amount reclassified from AOCI, net of tax									9	41	(14)
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	367	178	517
Other comprehensive income (loss) before reclassifications									(93)	196	(309)
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)									(107)	189	(339)
Balance at end of period	260				367				260	367	178
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)									(11)	(12)	(43)
Net investment income									(9)
Interest expense									0	0	0
Total before tax									(20)	(12)	(43)
Total (provision) benefit for income taxes									6	5	13
Total amount reclassified from AOCI, net of tax									(14)	(7)	(30)
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)	4	(24)	(5)
Other comprehensive income (loss) before reclassifications									(43)	(20)	(35)
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)									(19)	28	(19)
Balance at end of period	(15)				4				(15)	4	(24)
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)									37	74	24
Net investment income									0
Interest expense									0	0	0
Total before tax									37	74	24
Total (provision) benefit for income taxes									(13)	(26)	(8)
Total amount reclassified from AOCI, net of tax									24	48	16
Accumulated Translation Adjustment [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period				(10)				(3)	(10)	(3)	(6)
Other comprehensive income (loss) before reclassifications									(6)	(7)	3
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)									(6)	(7)	3
Balance at end of period	(16)				(10)				(16)	(10)	(3)
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
Net investment income									0
Interest expense									0	0	0
Total before tax									0	0	0
Total (provision) benefit for income taxes									0	0	0
Total amount reclassified from AOCI, net of tax									0	0	0
Cash Flow Hedge [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period				$ 9				$ 9	9	9	9
Other comprehensive income (loss) before reclassifications									0	0	0
Amounts reclassified from AOCI to:
Net current period other comprehensive income (loss)									(1)	0	0
Balance at end of period	$ 8				$ 9				8	9	9
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
Net investment income									0
Interest expense									(1)	0	(1)
Total before tax									(1)	0	(1)
Total (provision) benefit for income taxes									0	0	1
Total amount reclassified from AOCI, net of tax									$ (1)	$ 0	$ 0