Investments (details) - OTTI Rollforward (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Roll-forward of the credit component of other-than-temporary impairments on fixed maturities recognized in the consolidated statement of income 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	$ 171	$ 160	$ 165	$ 152
Additions for OTTI securities where credit losses have been previously recognized		1	2	7
Reductions due to sales/defaults of credit-impaired securities		(1)		(1)
Adjustments to book value of credit-impaired securities due to changes in cash flows	3	2	7	4
Cumulative OTTI credit losses recognized for securities still held, end of period	174	162	174	162
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 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	67	61	63	58
Additions for OTTI securities where credit losses have been previously recognized			2	3
Reductions due to sales/defaults of credit-impaired securities		(1)		(1)
Adjustments to book value of credit-impaired securities due to changes in cash flows	2	1	4	1
Cumulative OTTI credit losses recognized for securities still held, end of period	69	61	69	61
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 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	104	99	102	94
Additions for OTTI securities where credit losses have been previously recognized		1		4
Adjustments to book value of credit-impaired securities due to changes in cash flows	1	1	3	3
Cumulative OTTI credit losses recognized for securities still held, end of period	$ 105	$ 101	$ 105	$ 101