Bank Credit Agreements and Other Short-Term and Long-Term Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total long-term debt	$ 270,083	$ 429,841
Current portion of long-term debt	(20,636)	(14,356)
Less: Unamortized debt issuance costs	(1,955)	(2,359)
Long-term debt, net of current portion	247,492	413,126
Notes Payable To Bank
Debt Instrument [Line Items]
Total long-term debt	1,271	1,466
Term Loan and Revolver
Debt Instrument [Line Items]
Total long-term debt	$ 268,812	$ 428,375