Investments (Net Investment Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 14,134	$ 13,531	$ 12,264
Less: investment expenses	(473)	(407)	(399)
Net Investment Income, Total	13,661	13,124	11,865
Available For Sale Fixed Maturities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	9,800	9,374	8,346
Fixed Maturities, Held To Maturity [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	135	140	150
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	332	315	285
Trading Account Assets [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	890	889	822
Commercial Mortgage Loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	2,014	1,926	1,887
Policy Loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	597	598	577
Broker Dealer Related Receivables [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	0	0	0
Short-term Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	46	58	45
Other Long-term Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 320	$ 231	$ 152