Investments (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Amortized cost
Due in one year or less	$ 2,749
Due after one year through five years	8,834
Due after five years through ten years	14,503
Due after ten years	11,623
Subtotal	37,709
RMBS and ABS	3,994
Total	41,703
Fair value
Due in one year or less	2,791
Due after one year through five years	9,480
Due after five years through ten years	16,137
Due after ten years	13,141
Subtotal	41,549
RMBS and ABS	3,906
Total	$ 45,455	$ 45,428