Investments (details) - OTTI Rollforward (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Roll-forward of the credit component of other-than-temporary impairments on fixed maturities recognized in the consolidated statement of income (loss) for which a portion of the other-than-temporary impairment was recognized in other comprehensive income [Roll Forward]
Cumulative OTTI credit losses recognized for securities held, beginning of period	$ 156	$ 139	$ 152	$ 135
Additions for OTTI securities where no credit losses were previously recognized				1
Additions for OTTI securities where credit losses have been previously recognized	3	3	6	6
Reductions due to sales/defaults of credit-impaired securities				(1)
Adjustments to book value of credit-impaired securities due to changes in cash flows	1	1	2	2
Cumulative OTTI credit losses recognized for securities still held, end of period	160	143	160	143
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Roll-forward of the credit component of other-than-temporary impairments on fixed maturities recognized in the consolidated statement of income (loss) for which a portion of the other-than-temporary impairment was recognized in other comprehensive income [Roll Forward]
Cumulative OTTI credit losses recognized for securities held, beginning of period	59	49	58	47
Additions for OTTI securities where credit losses have been previously recognized	2	2	3	4
Cumulative OTTI credit losses recognized for securities still held, end of period	61	51	61	51
All other corporate bonds [Member]
Roll-forward of the credit component of other-than-temporary impairments on fixed maturities recognized in the consolidated statement of income (loss) for which a portion of the other-than-temporary impairment was recognized in other comprehensive income [Roll Forward]
Cumulative OTTI credit losses recognized for securities held, beginning of period	97	90	94	88
Additions for OTTI securities where no credit losses were previously recognized				1
Additions for OTTI securities where credit losses have been previously recognized	1	1	3	2
Reductions due to sales/defaults of credit-impaired securities				(1)
Adjustments to book value of credit-impaired securities due to changes in cash flows	1	1	2	2
Cumulative OTTI credit losses recognized for securities still held, end of period	$ 99	$ 92	$ 99	$ 92