Long-Term Debt and Related Matters (Schedule Of Long-Term Debt Table) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Long-Term Debt and Related Matters [Abstract]
Revolving credit facility with an interest rate of 4.16% at December 31, 2016 and 2.10% at December 31, 2015.	$ 127,073	$ 165,000
Term loan payable in quarterly installments through January 1, 2020 with an interest rate of 3.92% at December 31, 2016	30,000	0
Financing agreement payable in installments through July 1, 2017 with an interest rate of 3.00% at December 31, 2015	534	1,247
Lease obligations payable in installments through 2019 with a weighted average interest rate of 3.10% at December 31, 2016 and 3.09% December 31, 2015	1,958	2,507
Total	159,565	168,754
Less current maturities	10,386	1,335
Long-term debt	$ 149,179	$ 167,419
Line of Credit Facility, Interest Rate at Period End	4.22%	2.10%
Accounts Payable, Interest-bearing, Interest Rate	3.00%
Long-term Debt, Weighted Average Interest Rate	3.10%	3.09%
Debt Instrument, Imputed Interest Rate at End of Period	3.92%