Investments (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Amortized cost
Due in one year or less	$ 4,017
Due after one year through five years	20,943
Due after five years through ten years	24,287
Due after ten years	16,138
Subtotal	65,385
RMBS and ABS	7,047
Total amortized cost for fixed income securities	72,432
Fair value
Due in one year or less	4,072
Due after one year through five years	22,124
Due after five years through ten years	26,615
Due after ten years	17,897
Subtotal	70,708
RMBS and ABS	7,021
Total fixed income securities	$ 77,729	$ 76,113