Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ (115,814)
Other comprehensive (loss) income		(19,084)	$ 40,579	$ (16,255)
Ending balance		(134,898)	(115,814)
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(7,056)	(34,896)
Other comprehensive income (loss), before reclassifications		(7,527)	27,840
Reclassification to net income		9,255	(27,840)
Ending balance		(14,583)	(7,056)	(34,896)
Pension and other post-retirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	(108,760)	(121,448)
Other comprehensive (loss) income	[1]	(11,559)	12,688
Ending balance	[1]	(120,319)	(108,760)	(121,448)
Amortization of net loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to net income	[1]	8,800	8,785
Reclassification from AOCI, tax		(2,818)	(5,304)
Change in net gain
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification to net income	[1]	(20,359)	3,903
Reclassification from AOCI, tax		6,519	(2,357)
Derivative instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[2]	2	(49)
Other comprehensive income (loss), before reclassifications	[2]	0	121
Reclassification to net income	[2]	2	(70)
Other comprehensive (loss) income	[2]	2	51
Ending balance	[2]	4	2	$ (49)
OCI before reclassifications to net income, tax		0	(73)
Reclassification from AOCI, tax		(1)	42
U.K. Composites [Member] | Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax		$ 1,728	$ 0

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 15, Pension Plans for additional information)

[2] See Note 7, Derivative Financial Instruments, for additional information regarding the Company's derivative instruments.