Other Comprehensive Income (Loss) Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances				$ 544,020
Total other comprehensive income (loss)		$ 1,910	$ 1,690	430		$ 4,040
Balances		585,690		585,690
Other Comprehensive Income (Loss), Tax [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax				(500)		100
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax				800		100
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax						100
Defined Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances				(10,450)		(12,120)
Net unrealized gains (losses) arising during the period				0		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(2,850)	[1]	(330)	[2]
Total other comprehensive income (loss)				2,850		330
Balances		(7,600)	(11,790)	(7,600)		(11,790)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances						(2,520)
Net unrealized gains (losses) arising during the period	[3]					(230)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[2]					(210)
Total other comprehensive income (loss)						(20)
Balances			(2,540)			(2,540)
Accumulated Net Gain (Loss) from Hedges Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances				(3,170)
Net unrealized gains (losses) arising during the period	[4]			1,670
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				0
Total other comprehensive income (loss)				1,670
Balances		(1,500)		(1,500)
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances				(3,710)		(9,760)
Net unrealized gains (losses) arising during the period				(4,090)		3,730
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				0		0
Total other comprehensive income (loss)				(4,090)		3,730
Balances		(7,800)	(6,030)	(7,800)		(6,030)
Accumulated Other Comprehensive Income [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balances				(17,330)		(24,400)
Net unrealized gains (losses) arising during the period				(2,420)		3,500
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(2,850)		(540)
Total other comprehensive income (loss)				430		4,040
Balances		$ (16,900)	$ (20,360)	$ (16,900)		$ (20,360)

[1] Defined benefit plans, net of income tax of approximately $0.8 million. See Note 14, "Defined Benefit Plans," for further details.

[2] Defined benefit plans, net of income tax of approximately $0.1 million. See Note 14, "Defined Benefit Plans," for further details. Derivative instruments, net of income tax of approximately $0.1 million. See Note 9, "Derivative Instruments," for further details.

[3] Derivative instruments, net of income tax of approximately $0.1 million. See Note 9, "Derivative Instruments," for further details.

[4] Derivative instruments, net of income tax of approximately $0.5 million. See Note 9, "Derivative Instruments," for further details.