Investments (details) - OTTI Rollforward (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 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	$ 168	$ 156	$ 165	$ 152
Additions for OTTI securities where credit losses have been previously recognized	1	3	2	6
Adjustments to book value of credit-impaired securities due to changes in cash flows	2	1	4	2
Cumulative OTTI credit losses recognized for securities still held, end of period	171	160	171	160
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	65	59	63	58
Additions for OTTI securities where credit losses have been previously recognized	1	2	2	3
Adjustments to book value of credit-impaired securities due to changes in cash flows	1		2
Cumulative OTTI credit losses recognized for securities still held, end of period	67	61	67	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	103	97	102	94
Additions for OTTI securities where credit losses have been previously recognized		1		3
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	$ 104	$ 99	$ 104	$ 99