Schedule I - Condensed Financial Information of the Parent (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Other, net									$ 2,988	$ 1,225	$ 277
Other (income) expense									7,245	7,028	10,264
Administrative and general expenses									197,903	193,925	198,697
Income (loss) before income tax provision (benefit)									34,470	24,799	(76,573)
Income tax benefit									4,863	2,815	(38,455)
Net income (loss)	$ 24,131	$ (442)	$ 3,116	$ 2,802	$ 18,091	$ 3,141	$ (275)	$ 1,027	29,607	21,984	(38,118)
Foreign currency translation adjustment									(2,078)	(2,756)	(1,896)
Deferred gain on available for sale securities, net of tax									413	17	442
Current period cash flow hedging activity, net of $73 tax benefit in 2016, $357 tax benefit in 2015 and $838 tax benefit in 2014									(252)	(577)	(1,518)
Reclassification of hedging activities into earnings, net of $419 tax benefit in 2016, $191 tax benefit in 2015 and $489 tax benefit in 2014									757	409	898
Current period pension and postretirement plan adjustment, net of $1,098 tax benefit in 2016, $1,222 tax benefit in 2015 and $3,292 tax benefit in 2014									(2,011)	(1,204)	(6,483)
Reclassification of pension and postretirement adjustments into earnings, net of $408 tax benefit in 2016, $420 tax benefit in 2015 and $313 tax benefit in 2014									688	856	627
Total other comprehensive loss									(2,483)	(3,255)	(7,930)
Comprehensive income (loss)									27,124	18,729	(46,048)
Current period cash flow hedging activity, tax benefit									(73)	(357)	(838)
Reclassification of hedging activities into earnings, tax benefit									(419)	(191)	(489)
Current period pension and postretirement plan adjustment, tax benefit									(1,098)	(1,222)	(3,292)
Reclassification of pension and post retirement adjustments into earnings, tax benefit									(408)	(420)	(313)
Parent Company
Condensed Financial Statements, Captions [Line Items]
Intercompany interest expense									1,285	1,309	1,305
Other, net									(332)	(270)	(276)
Other (income) expense									953	1,039	1,029
Administrative and general expenses									6,881	3,704	4,862
Income (loss) before income tax provision (benefit)									(7,834)	(4,743)	(5,891)
Income tax benefit									(2,295)	(1,496)	(1,764)
Net loss before equity in earnings of subsidiaries									(5,539)	(3,247)	(4,127)
Equity in earnings of subsidiaries									35,146	25,231	(33,991)
Net income (loss)									29,607	21,984	(38,118)
Foreign currency translation adjustment									(2,078)	(2,756)	(1,896)
Deferred gain on available for sale securities, net of tax									413	17	442
Current period cash flow hedging activity, net of $73 tax benefit in 2016, $357 tax benefit in 2015 and $838 tax benefit in 2014									(252)	(577)	(1,518)
Reclassification of hedging activities into earnings, net of $419 tax benefit in 2016, $191 tax benefit in 2015 and $489 tax benefit in 2014									757	409	898
Current period pension and postretirement plan adjustment, net of $1,098 tax benefit in 2016, $1,222 tax benefit in 2015 and $3,292 tax benefit in 2014									(2,011)	(1,204)	(6,483)
Reclassification of pension and postretirement adjustments into earnings, net of $408 tax benefit in 2016, $420 tax benefit in 2015 and $313 tax benefit in 2014									688	856	627
Total other comprehensive loss									(2,483)	(3,255)	(7,930)
Comprehensive income (loss)									27,124	18,729	(46,048)
Current period cash flow hedging activity, tax benefit									(73)	(357)	(838)
Reclassification of hedging activities into earnings, tax benefit									(419)	(191)	(489)
Current period pension and postretirement plan adjustment, tax benefit									(1,098)	(1,222)	(3,292)
Reclassification of pension and post retirement adjustments into earnings, tax benefit									$ (408)	$ (420)	$ (313)