Debt (Principal Payments Due Under Medium-Term Note Obligations Based On Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Debt Instrument [Line Items]
Total expected principal payments	$ 901		$ 907
Discounts	1		1
Medium-Term Notes [Member]
Debt Instrument [Line Items]
2012	89
2013	41
2014	61
2015	253
2016	123
Thereafter	1,893
Total expected principal payments	2,460	[1]
Less discount and other adjustments	804	[2]
Total	1,656
Discounts	773
Fair value adjustments	41
Accrued interest	$ 10

[1] Foreign currency denominated medium-term notes are presented in U.S. dollars. Amounts reflect principal due at maturity for notes issued at a discount or premium.

[2] Includes discounts of $773 million and fair value adjustments of $41 million, net of accrued interest of $10 million.