Investments (Details 2) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Amortized cost
Total fixed maturities	$ 7,384
Estimated fair value
Total fixed maturities	7,848	7,543
Indemnity
Amortized cost
Due in one year or less	152
Due after one year through five years	219
Due after five years through ten years	48
Due after ten years	88
Total fixed maturities	507
Estimated fair value
Due in one year or less	152
Due after one year through five years	222
Due after five years through ten years	51
Due after ten years	92
Total fixed maturities	517	264
Exchange
Amortized cost
Due in one year or less	449
Due after one year through five years	2,451
Due after five years through ten years	2,722
Due after ten years	1,255
Total fixed maturities	6,877
Estimated fair value
Due in one year or less	457
Due after one year through five years	2,576
Due after five years through ten years	2,949
Due after ten years	1,349
Total fixed maturities	$ 7,331	$ 7,279