Long-Term Debt (Schedule of Long-Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt	$ 60,082	$ 70,090
Less current maturities	82	73
Total long-term debt	60,000	70,017
Capital lease obligations
Debt Instrument [Line Items]
Total debt	0	0
Other notes payable
Debt Instrument [Line Items]
Total debt	82	90
Bank revolving credit facility | Amended and Restated Revolving Credit Agreement | Unsecured Debt
Debt Instrument [Line Items]
Total debt	$ 60,000	$ 70,000