Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Mar. 31, 2012
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period			$ 515
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other comprehensive income (loss)	(3)	101	(309)	163
Balance at end of period	206		206
Net Unrealized Gains (Losses) on Investments with no OTTI
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	237		517	365	445
Other comprehensive income (loss) before reclassifications	(11)		(280)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	(2)		(16)
Interest expense	0		0
Total before tax	(2)		(16)
Tax (provision) benefit	1		4
Total amounts reclassified from AOCI, net of tax	(1)		(12)
Other comprehensive income (loss)	(12)	94	(292)	174
Balance at end of period	225	539	225	539	445
Net Unrealized Gains (Losses) on Investments with OTTI
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(25)		(5)	2	(16)
Other comprehensive income (loss) before reclassifications	(2)		(34)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	7		24
Interest expense	0		0
Total before tax	7		24
Tax (provision) benefit	(3)		(8)
Total amounts reclassified from AOCI, net of tax	4		16
Other comprehensive income (loss)	2	5	(18)	(13)
Balance at end of period	(23)	(11)	(23)	(11)	(16)
Cumulative Translation Adjustment
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(12)		(6)	(8)	(8)
Other comprehensive income (loss) before reclassifications	7		1
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	0		0
Interest expense	0		0
Total before tax	0		0
Tax (provision) benefit	0		0
Total amounts reclassified from AOCI, net of tax	0		0
Other comprehensive income (loss)	7	2	1	2
Balance at end of period	(5)	(6)	(5)	(6)	(8)
Cash Flow Hedge
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	9		9	9	9
Other comprehensive income (loss) before reclassifications	0		0
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	0		0
Interest expense	0		(1)
Total before tax	0		(1)
Tax (provision) benefit	0		1
Total amounts reclassified from AOCI, net of tax	0		0
Other comprehensive income (loss)	0	0	0	0
Balance at end of period	9	9	9	9	9
Total Accumulated Other Comprehensive Income
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	209		515	368	430
Other comprehensive income (loss) before reclassifications	(6)		(313)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	5		8
Interest expense	0		(1)
Total before tax	5		7
Tax (provision) benefit	(2)		(3)
Total amounts reclassified from AOCI, net of tax	3		4
Other comprehensive income (loss)	(3)	101	(309)	163
Balance at end of period	$ 206	$ 531	$ 206	$ 531	$ 430