Accumulated Other Comprehensive Income (Details) (USD $) In Millions	9 Months Ended			12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010		Dec. 31, 2010	Dec. 31, 2009
Accumulated Other Comprehensive Income
Currency translation adjustments, beginning balance, net of tax	$ 171	$ 166		$ 166
Unrealized gains / (losses) on cash flows hedges, net, beginning balance, net of tax	(15)	(27)		(27)
Minimum pension liability adjustment, beginning balance, net of tax	(1)	(1)		(1)
Accumulated other comprehensive income, beginning balance, net of tax	155	138		138
Currency translation adjustment, net of tax	(25)	1
Unrealized gains / (losses) on cash flows hedges, net, current period change	3	10	[1]
Minimum pension liability adjustment, current period change
Accumulated other comprehensive income, current period change	(22)	11
Currency translation adjustments, ending balance, net of tax	146	167		171	166
Unrealized gains / (losses) on cash flows hedges, net, ending balance, net of tax	(12)	(17)		(15)	(27)
Minimum pension liability adjustment, ending balance, net of tax	(1)	(1)		(1)	(1)
Accumulated other comprehensive income, ending balance, net of tax	133	149		155	138
Tax effect in accumulated other comprehensive income	$ 40	$ 39		$ 40	$ 32

[1] Primarily represents the reclassification of an after-tax unrealized loss associated with the termination of an interest rate swap agreement in connection with the early extinguishment of the term loan facility (see Note 7—Long-Term Debt and Borrowing Arrangements).