Long-Term Debt (Schedule of Long-Term Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Mar. 31, 2013
Debt Instrument [Line Items]
Less unamortized debt issuance costs	$ (2,575)	$ (3,163)
Total debt	(209,825)	(209,637)
Less current maturities	400	400
Total long-term debt	209,425	209,237
Senior Subordinated 6.25% Notes
Debt Instrument [Line Items]
Total debt	$ (210,000)	$ (210,000)
Senior Subordinated Notes, interest rate	6.25%	6.25%	6.25%
Other debt
Debt Instrument [Line Items]
Total debt	$ (2,400)	$ (2,800)