Debt Schedule of Outstanding Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes Payable to Bank	$ 3,926
Current Portion of Long-Term Debt	27,005	$ 30,883
Debt and Capital Lease Obligations	355,065	376,839
Less: Unamortized Debt Issuance Costs	(4,724)	(6,440)
Less: Current Maturities of Capital Lease Obligations	(1,262)
Long-Term Debt	328,060	345,956
Bonds
Debt Instrument [Line Items]
Debt and Capital Lease Obligations	300,000	300,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt and Capital Lease Obligations	2,863	3,279
Line of Credit [Member]
Debt Instrument [Line Items]
Current Portion of Long-Term Debt	25,927
Less: Current Maturities of Credit Facility Borrowings, Net of Debt Issuance Costs	(27,005)	(30,883)
Debt Instrument, Unamortized Debt Issuance Costs, Current Portion, net	184
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt, Additional Repayments of Principal in Next Twelve Months	15,125
Debt Instrument, Unused Borrowing Capacity, Amount	165,721
JPMorgan, 2017 Credit Agreement \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt and Capital Lease Obligations	$ 53,000	$ 80,000

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