Debt (Principal Payments Due Under Investment Agreement Obligations) (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
Investment Agreement Obligations [Member]
Debt Instrument [Line Items]
2012	471
2013	182
2014	140
2015	171
2016	53
Thereafter	671
Total expected principal payments	1,688	[1]
Less discount and other adjustments	110	[2]
Total, Principal Amount	1,578
Discounts	153
Fair value adjustments	33
Accrued interest	$ 10

[1] Foreign currency denominated investment agreements are presented in U.S. dollars. Amounts reflect principal due at maturity for investment agreements issued at a discount.

[2] Includes discounts of $153 million on investment agreements, net fair value adjustments of $33 million and accrued interest of $10 million.