Debt and Credit Agreements (Details 3) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total debt obligations	$ 593,659	$ 673,410
Less: deferred financing costs	(15,657)	(18,597)
Total debt obligations, net of deferred financing costs	578,002	654,813
Less: current maturities of long-term debt	(11,208)	(25,574)
Long-term debt	566,794	629,239
Maturities of Long-term Debt [Abstract]
2019	6,274
2020	5,640
2021	46,498
2022	5,459
Revolving Credit Facility
Debt Instrument [Line Items]
Total debt obligations	$ 41,000	$ 98,000
Variable interest rate	4.20%	3.60%
Term Loan
Debt Instrument [Line Items]
Total debt obligations	$ 545,875	$ 550,000
Variable interest rate	4.60%	6.00%
Other financing payable in varying amounts due principally through 2018 with a weighted-average interest rate of 2.7% and 9.4% at December 31, 2012 and 2011, respectively
Debt Instrument [Line Items]
Total debt obligations	$ 6,784	$ 25,410
Weighted average interest rate	5.00%	5.70%