Segments (Narrative) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Company's revenue, percentage	11.00%	11.00%	10.00%
Percentage of revenue, single geographic business in United Kingdom and Czech Republic represent of consolidated revenues	10.00%	10.00%	10.00%
Percentage of long-lived assets (excluding goodwill), single geography represented threshold	10.00%	10.00%
Chevron [Member]
Segment Reporting Information [Line Items]
Company's revenue, percentage	11.00%	11.00%
North America [Member]
Segment Reporting Information [Line Items]
Number of customers with concentration risk	2	2	2
Company's revenue, percentage	29.50%	30.80%	25.10%