Business Realignment and Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	$ 21	$ 1,621	$ 220	$ 1,628
Additional restructuring costs	19		19
Particulate Matter Product Line Strategic Exit [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			1,654	2,552
Particulate Matter Product Line Strategic Exit [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	285	2,552	1,654	2,552
Particulate Matter Product Line Strategic Exit [Member] \| Control Devices [Member] \| Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Estimated total cost	1,700		1,700
Particulate Matter Product Line Strategic Exit [Member] \| Control Devices [Member] \| Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Estimated total cost	4,900		4,900
Canton Facility Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			13	2,683
Canton Facility Restructuring Plan [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	0	461
Employee Termination [Member] \| Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			50	863
Employee Termination [Member] \| Particulate Matter Product Line Strategic Exit [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			76
Employee Termination [Member] \| Canton Facility Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense				1,119
Fixed Asset Impairment [Member] \| Particulate Matter Product Line Strategic Exit [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense				2,482
Other Restructuring [Member] \| Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			170	313
Other Restructuring [Member] \| Particulate Matter Product Line Strategic Exit [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			1,393	70
Other Restructuring [Member] \| Canton Facility Restructuring Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			13	1,564
Contract Termination [Member] \| Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense				452
Selling, General and Administrative Expenses [Member] \| Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	19	1,244	174	1,251
Selling, General and Administrative Expenses [Member] \| Particulate Matter Product Line Strategic Exit [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	35	2,388	673	2,388
Selling, General and Administrative Expenses [Member] \| Canton Facility Restructuring Plan [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense		235		549
Cost of Goods Sold [Member] \| Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	5		3
Cost of Goods Sold [Member] \| Particulate Matter Product Line Strategic Exit [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	250	164	900	164
Cost of Goods Sold [Member] \| Canton Facility Restructuring Plan [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense		80		1,570
Design and Development Expense [Member] \| Electronics [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense	$ (3)	377	43	377
Design and Development Expense [Member] \| Particulate Matter Product Line Strategic Exit [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			81
Design and Development Expense [Member] \| Canton Facility Restructuring Plan [Member] \| Control Devices [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense		$ 146	$ 13	$ 564