Investments (Trading Account Assets Supporting Insurance Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Amortized Cost	$ 19,249		$ 18,829
Fair Value	20,590	[1]	19,481	[1]
Cash Equivalents And Short Term Investments [Member]
Amortized Cost	938		951
Fair Value	938		951
Fixed Maturities [Member]
Amortized Cost	17,368		16,828	[2]
Fair Value	18,612		17,619	[2]
Fixed Maturities [Member] | Foreign Government Debt Securities [Member]
Amortized Cost	683		599	[2]
Fair Value	708		608	[2]
Fixed Maturities [Member] | Corporate Debt Securities [Member]
Amortized Cost	11,076		10,369	[2]
Fair Value	12,107		11,113	[2]
Fixed Maturities [Member] | Asset-backed Securities [Member]
Amortized Cost	1,179		1,504
Fair Value	1,116		1,367
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Amortized Cost	2,096		2,157
Fair Value	2,229		2,247
Fixed Maturities [Member] | Residential Mortgage Backed Securities [Member]
Amortized Cost	1,965	[3]	1,786	[3]
Fair Value	2,026	[3]	1,844	[3]
Fixed Maturities [Member] | US Government Corporations and Agencies Securities [Member]
Amortized Cost	369		413	[2]
Fair Value	426		440	[2]
Equity Securities [Member]
Amortized Cost	943		1,050
Fair Value	$ 1,040		$ 911

[1] (1) See Note 5 for details of balances associated with variable interest entities.

[2] Prior period’s amounts are presented on a basis consistent with the current period presentation.

[3] Includes publicly-traded agency pass-through securities and collateralized mortgage obligations. Includes credit-tranched securities collateralized by sub-prime mortgages, auto loans, credit cards, education loans and other asset types. Prior period’s amounts are presented on a basis consistent with the current period presentation.