Investments (Details 2) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Amortized cost
Due in one year or less	$ 2,816
Due after one year through five years	25,101
Due after five years through ten years	22,450
Due after ten years	10,945
Subtotal	61,312
ABS, RMBS and CMBS	7,163
Total amortized cost for fixed income securities	68,475
Fair value
Due in one year or less	2,859
Due after one year through five years	25,901
Due after five years through ten years	23,243
Due after ten years	11,784
Subtotal	63,787
ABS, RMBS and CMBS	7,252
Total fixed income securities	$ 71,039	$ 77,017