Investments (Contractual Maturity Dates For Fixed-Maturity And Short-Term Investments) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Amortized cost
Due in one year or less	$ 453
Due after one year through five years	3,068
Due after five years through ten years	3,592
Due after ten years	2,211
Total	9,324	$ 8,871
Fair value
Due in one year or less	459
Due after one year through five years	3,243
Due after five years through ten years	3,649
Due after ten years	2,299
Total	$ 9,650	$ 9,460
% of fair value
Due in one year or less	4.80%
Due after one year through five years	33.60%
Due after five years through ten years	37.80%
Due after ten years	23.80%
Total	100.00%