Investments (Maturities of Fixed Maturity Securities) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale Securities, Debt Maturities [Abstract]
Amortized Cost, Due in one year or less	$ 5,841	$ 6,411
Amortized Cost, Due after one year through five years	36,600	34,696
Amortized Cost, Due after five years through ten years	39,257	35,725
Amortized Cost, Due after ten years	49,102	48,428
Amortized Cost, RMBS, CMBS and ABS	42,804	40,111
Amortized Cost, Subtotal	173,604	165,371
Estimated Fair Value, Due in one year or less	5,902	6,516
Estimated Fair Value, Due after one year through five years	38,115	36,556
Estimated Fair Value, Due after five years through ten years	41,519	38,347
Estimated Fair Value, Due after ten years	59,073	51,417
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis	130,800	125,260
Estimated Fair Value, Subtotal	144,609	132,836
Estimated fair value, Mortgage-backed and asset-backed securities	44,302	40,910
Fixed maturity securities available-for-sale, at estimated fair value (amortized cost: $173,604 and $165,371, respectively; includes $160 and $157, respectively, relating to variable interest entities)	$ 188,911	$ 173,746