Description of Business (Details)	12 Months Ended
	Dec. 31, 2011 operating_segments countries_and_territiories
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Approximate number of system units	37,000
Percent of system units located outside the U.S. (in hundredths)	50.00%
Approximate number of countries and territories where system units are located	120
Segment Reporting Information [Line Items]
Number of operating segments	5
U.S.
Segment Reporting Information [Line Items]
Number of operating segments	3