Accumulated Other Comprehensive Income (Loss) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	$ (48,061)
Other comprehensive income before reclassifications	7,922
Amounts reclassified from AOCI	570
Balance at March 31, 2018	(39,569)
Pension and Other Post-Retirement Benefit Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(45,812)
Other comprehensive income before reclassifications	0
Amounts reclassified from AOCI	(46)
Balance at March 31, 2018	(45,858)
Cash Flow Hedging Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(293)
Other comprehensive income before reclassifications	7,487
Amounts reclassified from AOCI	616
Balance at March 31, 2018	7,810
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(1,956)
Other comprehensive income before reclassifications	435
Amounts reclassified from AOCI	0
Balance at March 31, 2018	$ (1,521)