Investments (Details 2) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Amortized cost
Total fixed maturities	$ 7,445
Estimated fair value
Total fixed maturities	7,905	7,543
Indemnity
Amortized cost
Due in one year or less	154
Due after one year through five years	220
Due after five years through ten years	54
Due after ten years	88
Total fixed maturities	516
Estimated fair value
Due in one year or less	154
Due after one year through five years	224
Due after five years through ten years	57
Due after ten years	90
Total fixed maturities	525	264
Exchange
Amortized cost
Due in one year or less	392
Due after one year through five years	2,469
Due after five years through ten years	2,798
Due after ten years	1,270
Total fixed maturities	6,929
Estimated fair value
Due in one year or less	401
Due after one year through five years	2,622
Due after five years through ten years	3,019
Due after ten years	1,338
Total fixed maturities	$ 7,380	$ 7,279