Investments (Available-For-Sale Fixed Maturity Securities By Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Investments [Abstract]
Amortized Cost, Due in one year or less	$ 1,842	$ 1,802
Amortized Cost, Due after one year through five years	13,003	13,110
Amortized Cost, Due after five years through ten years	8,713	8,410
Amortized Cost, Due after ten years	14,240	14,017
Amortized Cost, Total	37,798	37,339
Estimated Fair Value, Due in one year or less	1,855	1,812
Estimated Fair Value, Due after one year through five years	13,573	13,537
Estimated Fair Value, Due after five years through ten years	9,326	8,890
Estimated Fair Value, Due after ten years	16,071	15,692
Estimated Fair Value, Total	$ 40,825	$ 39,931