Reserve for Life-Contingent Contract Benefits and Contractholder Funds (Details 2) (USD $) In Millions, unless otherwise specified				12 Months Ended		12 Months Ended						12 Months Ended									12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Interest-sensitive life insurance	Dec. 31, 2011 Interest-sensitive life insurance	Dec. 31, 2012 Equity-indexed life insurance Minimum	Dec. 31, 2012 Equity-indexed life insurance Maximum	Dec. 31, 2012 Other life insurance Minimum	Dec. 31, 2012 Other life insurance Maximum	Dec. 31, 2012 Fixed annuities	Dec. 31, 2011 Fixed annuities	Dec. 31, 2012 Fixed annuities Maximum	Dec. 31, 2012 Immediate fixed annuities Minimum	Dec. 31, 2012 Immediate fixed annuities Maximum	Dec. 31, 2012 Equity indexed fixed annuities Minimum	Dec. 31, 2012 Equity indexed fixed annuities Maximum	Dec. 31, 2012 Other fixed annuities Minimum	Dec. 31, 2012 Other fixed annuities Maximum	Dec. 31, 2012 Funding agreements backing medium-term notes	Dec. 31, 2011 Funding agreements backing medium-term notes	Dec. 31, 2012 Funding agreements backing medium-term notes Minimum	Dec. 31, 2012 Funding agreements backing medium-term notes Maximum	Dec. 31, 2012 Other investment contracts	Dec. 31, 2011 Other investment contracts	Dec. 31, 2012 Other investment contracts Minimum	Dec. 31, 2012 Other investment contracts Maximum
Contractholder funds
Total contractholder funds	$ 39,319	$ 42,332	$ 48,195	$ 11,011	$ 10,826					$ 25,881	$ 29,049								$ 1,867	$ 1,929			$ 560	$ 528
Key contract provisions relating to contractholder funds:
Contractholder funds, interest rate assumptions (as a percent)						0.00%	11.00%	1.00%	6.00%				0.00%	9.80%	(8.00%)	13.50%	0.10%	6.30%			3.00%	5.40%			1.70%	10.30%
Period for withdrawal or surrender charges				20 years								10 years
Percent of fixed annuities subject to market value adjustment for discretionary withdrawals										24.30%