Stockholders' Equity Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	[1]			$ (14,959)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				(1,894)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(377)
Other Comprehensive Income (Loss), Net of Tax		$ (19,484)	$ 9,856	(2,271)	$ 11,885
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent				(5)
Accumulated Other Comprehensive Income (Loss), Net of Tax		(17,230)		(17,230)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax				(14,578)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				(2,290)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				0
Other Comprehensive Income (Loss), Net of Tax				(2,290)
Accumulated Other Comprehensive Income (Loss), Net of Tax		(16,868)		(16,868)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax				(365)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax				391
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax				(377)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent				14
Accumulated Other Comprehensive Income (Loss), Net of Tax		(351)		(351)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax				(16)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax				5
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax				0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent				5
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ (11)		$ (11)

[1] December 31, 2017 balances were derived from audited consolidated financial statements.