Investments (Details 2) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Amortized cost
Due in one year or less	$ 1,630
Due after one year through five years	8,399
Due after five years through ten years	15,283
Due after ten years	9,077
Subtotal	34,389
ABS, RMBS and CMBS	4,105
Total	38,494
Fair value
Due in one year or less	1,663
Due after one year through five years	8,934
Due after five years through ten years	15,866
Due after ten years	9,844
Subtotal	36,307
ABS, RMBS and CMBS	4,133
Total	$ 40,440	$ 44,876