Accumulated Other Comprehensive Income (Loss) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	$ (48,061)
Other comprehensive income before reclassifications	6,203
Amounts reclassified from AOCI	858
Balance at June 30, 2018	(41,000)
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	(3,827)
Amounts reclassified from AOCI	(83)
Balance at June 30, 2018	(49,722)
Cash Flow Hedging Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at December 31, 2017	(293)
Other comprehensive income before reclassifications	10,297
Amounts reclassified from AOCI	941
Balance at June 30, 2018	10,945
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	(267)
Amounts reclassified from AOCI	0
Balance at June 30, 2018	$ (2,223)