Debt Schedule Of Components Of Debt (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Long-term Debt	$ 252,705,000	$ 252,174,000
Less current portion	673,000	620,000
Total long-term debt	252,032,000	251,554,000
Senior Notes [Member] | 250 Million Senior Notes [Member]
Long-term Debt	249,444,000	249,379,000
Debt instruments effective interest rate	6.19%
Debt Instrument, Unamortized Discount	600,000	600,000
Line of Credit [Member] | Revolver [Member]
Long-term Debt	0	200,000
Debt instruments effective interest rate		0.675%
Capital Lease Obligations [Member]
Long-term Debt	3,172,000	2,538,000
Debt instruments effective interest rate	3.18%
Capital Lease Maturity Year	2016
Notes Payable, Other Payables [Member]
Long-term Debt	$ 89,000	$ 57,000