Supplemental Cash Flow and Other Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Supplemental Cash Flow Elements (Textual) [Abstract]
Capital expenditures	$ 3,700,000	$ 2,300,000	$ 1,400,000
Accrued liabilities	47,443,000	43,234,000
Employee incentives	19,700,000	15,400,000
Estimated obligation	$ 8,200,000
Estimation period	1 year