Investments (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Amortized cost
Due in one year or less	$ 3,825
Due after one year through five years	23,168
Due after five years through ten years	23,808
Due after ten years	12,981
Subtotal	63,782
ABS, RMBS and CMBS	8,133
Total amortized cost for fixed income securities	71,915
Fair value
Due in one year or less	3,872
Due after one year through five years	24,324
Due after five years through ten years	25,973
Due after ten years	14,694
Subtotal	68,863
ABS, RMBS and CMBS	8,154
Total fixed income securities	$ 77,017	$ 76,113