Restructuring and Exit Costs (Narrative) (Details) ft² in Thousands, $ in Thousands	3 Months Ended		12 Months Ended			15 Months Ended	18 Months Ended
	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2015 ft²	Dec. 31, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs	$ 1,300	$ 1,000	$ 2,282	$ 297	$ 2,512
September 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			1,275
Amount paid in restructuring expenses			431
Restructuring liability			817	0
February 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			997
Amount paid in restructuring expenses			855
Restructuring liability			0	0
Consolidation of US Manufacturing Operations
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			179	451	2,647	$ 3,000
Accelerated depreciation expense				100	400	600
Amount paid in restructuring expenses				453	1,010		$ 1,500
Restructuring liability			670	802	1,337				$ 0
Consolidation of US Manufacturing Operations | Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			179	86	1,208	1,500
Amount paid in restructuring expenses				0	0
Square feet of manufacturing facility | ft²								60
Restructuring liability			670	802	1,043				0
Consolidation of US Manufacturing Operations | Facility Closing | Accounts Payable and Accrued Liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring liability			300
Consolidation of US Manufacturing Operations | Facility Closing | Other Noncurrent Liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring liability			400
Consolidation of US Manufacturing Operations | Employee Severance Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			0	67	1,439	1,200
Amount paid in restructuring expenses				207	1,010
Restructuring liability			0	0	294				0
Consolidation of US Manufacturing Operations | Other Exit Costs
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			0	298	0	$ 300
Amount paid in restructuring expenses				246	0
Restructuring liability			0	0	0				$ 0
Restructuring Charges [Member] | September 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			1,200
Restructuring Charges [Member] | February 2017 Plan
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			900
Restructuring Charges [Member] | Consolidation of US Manufacturing Operations
Restructuring Cost and Reserve [Line Items]
Restructuring and exit costs			$ 200	$ 300	$ 2,500