Investments (Contractual Maturity) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Investments [Abstract]
Amortized Cost, Due in one year or less	$ 1,658	$ 1,515
Amortized Cost, Due after one year through five years	12,947	11,198
Amortized Cost, Due after five years through ten years	8,447	10,034
Amortized Cost, Due after ten years	13,852	13,686
Amortized Cost, Total	36,904	36,433
Estimated Fair Value, Due in one year or less	1,662	1,506
Estimated Fair Value, Due after one year through five years	13,407	11,653
Estimated Fair Value, Due after five years through ten years	8,941	10,437
Estimated Fair Value, Due after ten years	15,437	13,987
Estimated Fair Value, Total	$ 39,447	$ 37,583