Investments (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Amortized cost
Due in one year or less	$ 1,085
Due after one year through five years	5,191
Due after five years through ten years	10,882
Due after ten years	8,017
Subtotal	25,175
ABS, RMBS and CMBS	2,621
Total	27,796
Fair value
Due in one year or less	1,111
Due after one year through five years	5,603
Due after five years through ten years	11,343
Due after ten years	8,595
Subtotal	26,652
ABS, RMBS and CMBS	2,683
Total	$ 29,335	$ 44,876