Accumulated Other Comprehensive Income (Loss) (Schedule of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Change in Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		$ (105,172)
Amounts reclassified from accumulated other comprehensive income (loss):
Ending balance		(98,889)
Foreign Currency Translation
Change in Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		(16,183)	$ (27,828)
Cumulative-effect adjustment for the adoption of ASU 2017-12				$ 0
Amounts reclassified from accumulated other comprehensive income (loss):
Amounts recognized into AOCI		4,333	1,408
Currency impact		0	0
Amounts reclassified from AOCI, Currency		0	0
Tax effect		0	0
Other comprehensive income (loss), net of tax		4,333	1,408
Ending balance		(11,850)	(26,420)
Derivative Instruments
Change in Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		351	(515)
Cumulative-effect adjustment for the adoption of ASU 2017-12				(275)
Amounts reclassified from accumulated other comprehensive income (loss):
Amounts recognized into AOCI		1,464	(266)
Currency impact		0	0
Amounts reclassified from AOCI, Derivatives	[1]	341	518
Tax effect		(335)	(87)
Other comprehensive income (loss), net of tax		1,470	165
Ending balance		1,546	(350)
Pension and Other Post-retirement Benefits
Change in Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		(89,340)	(96,854)
Cumulative-effect adjustment for the adoption of ASU 2017-12				0
Amounts reclassified from accumulated other comprehensive income (loss):
Amounts recognized into AOCI		0	0
Currency impact		(484)	(480)
Amounts reclassified from AOCI, Pension/PRW	[2]	1,606	1,464
Tax effect		(367)	(528)
Other comprehensive income (loss), net of tax		755	456
Ending balance		(88,585)	(96,398)
Accumulated Other Comprehensive Loss
Change in Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		(105,172)	(125,197)
Cumulative-effect adjustment for the adoption of ASU 2017-12				$ (275)
Amounts reclassified from accumulated other comprehensive income (loss):
Amounts recognized into AOCI		5,797	1,142
Currency impact		(484)	(480)
Amounts reclassified from AOCI		1,947	1,982
Tax effect		(702)	(615)
Other comprehensive income (loss), net of tax		6,558	2,029
Ending balance		$ (98,889)	$ (123,168)

[1] We reclassified natural gas contracts through cost of sales and the interest rate swap through interest expense on the Condensed Consolidated Statements of Operations. See note 8 for additional information.

[2] We reclassified the net pension and non-pension post-retirement benefits amortization and settlement charges through other income (expense) on the Condensed Consolidated Statements of Operations. See note 6 for additional information.