Long-Term Debt (Schedule Of Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified			12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Senior Subordinated Notes Due September 2018 [Member]	Aug. 31, 2010 Senior Subordinated Notes Due September 2018 [Member]	Dec. 31, 2011 Senior Subordinated Series A Notes [Member]	Dec. 31, 2011 Revolving Credit Facility [Member] Line of Credit [Member]	Dec. 31, 2010 Revolving Credit Facility [Member] Line of Credit [Member]
Debt Instrument [Line Items]
8.25% Senior subordinated notes due September 2018	$ 200,000	$ 200,000		$ 200,000
Revolving credit facility, including swing-line credit facility	166,000	46,200
Equipment financing notes	4,949	8,633
Total	370,949	254,833
Less: current portion	2,317	3,076
Total long-term debt, excluding current portion	$ 368,632	$ 251,757
Weighted-average combined rate						2.70%	3.10%
Senior subordinated notes stated interest percentage			8.25%	8.25%	9.25%
Maturity date			Sep. 01, 2018