Long-Term Debt (Debt Schedule) (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Mar. 10, 2015
Debt Instrument [Line Items]
Principal amount	$ 308,542,000
Line of Credit | Term Loan
Debt Instrument [Line Items]
Principal amount	308,542,000	$ 342,221,000	$ 350,000,000
Unamortized original issue discount and debt costs	(5,918,000)	(7,599,000)	$ (3,500,000)
Less: Current portion of long-term debt	(22,243,000)	(33,767,000)
Long-term debt	$ 280,381,000	$ 300,855,000