Accumulated Other Comprehensive (Loss) Income - Activity in AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (186,924)
Other comprehensive (loss) income	(938)	$ 3,616
Ending balance	641,988
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(230)
Other comprehensive (loss) income	(938)
Ending balance	(1,168)	(6,928)
Pension and other postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(7,126)	(12,880)
Other comprehensive (loss) income	499	729
Ending balance	(6,627)	(12,151)
Pension and other postretirement benefits, gain (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive (loss) income, before reclassifications, before tax	491	676
Other comprehensive (loss) income, before reclassifications, tax	0	0
Other comprehensive (loss) income, before reclassifications	491	676
Pension and other postretirement benefits, prior service cost
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassifications, before tax	8	53
Reclassifications, tax	0	0
Reclassifications	8	53
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	8,318	3,874
Other comprehensive (loss) income, before tax	(1,473)	3,235
Other comprehensive (loss) income, tax	0	0
Other comprehensive (loss) income	(1,473)	3,235
Ending balance	6,845	7,109
Cash flow hedge derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,422)	(1,538)
Other comprehensive (loss) income, before reclassifications, before tax	(314)	(869)
Other comprehensive (loss) income, before reclassifications, tax	15	(145)
Other comprehensive (loss) income, before reclassifications	(329)	(724)
Reclassifications	365	376
Ending balance	$ (1,386)	$ (1,886)