Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	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)	(68)	31
Balance at end of period	447
Net Unrealized Gains (Losses) on Investments with no OTTI
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	517	365
Other comprehensive income (loss) before reclassifications	(50)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	(1)
Interest expense	0
Total before tax	(1)
Tax (provision) benefit	0
Total amounts reclassified from AOCI, net of tax	(1)
Other comprehensive income (loss)	(51)	43
Balance at end of period	466	408
Net Unrealized Gains (Losses) on Investments with OTTI
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(5)	2
Other comprehensive income (loss) before reclassifications	(16)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	6
Interest expense	0
Total before tax	6
Tax (provision) benefit	(2)
Total amounts reclassified from AOCI, net of tax	4
Other comprehensive income (loss)	(12)	(14)
Balance at end of period	(17)	(12)
Cumulative Translation Adjustment
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	(6)	(8)
Other comprehensive income (loss) before reclassifications	(5)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	0
Interest expense	0
Total before tax	0
Tax (provision) benefit	0
Total amounts reclassified from AOCI, net of tax	0
Other comprehensive income (loss)	(5)	2
Balance at end of period	(11)	(6)
Cash Flow Hedge
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	9	9
Other comprehensive income (loss) before reclassifications	0
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	0
Interest expense	0
Total before tax	0
Tax (provision) benefit	0
Total amounts reclassified from AOCI, net of tax	0
Other comprehensive income (loss)	0	0
Balance at end of period	9	9
Total Accumulated Other Comprehensive Income
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Balance at beginning of period	515	368
Other comprehensive income (loss) before reclassifications	(71)
Amounts Reclassified Out Of Other Comprehensive Income [Abstract]
Other net realized investment gains (losses)	5
Interest expense	0
Total before tax	5
Tax (provision) benefit	(2)
Total amounts reclassified from AOCI, net of tax	3
Other comprehensive income (loss)	(68)	31
Balance at end of period	$ 447	$ 399