Restructuring Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 625	$ 1,431	$ 1,361
Total COGS and SGA
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	600	1,400	1,361
Surveillance
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0	107	226
Instruments
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	23	492	1,170
Security
Restructuring Cost and Reserve [Line Items]
Restructuring expenses		0	0
OEM & Emerging Markets [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0	65	(22)
Detection
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0	0	(13)
2013 Realignment Program | Total COGS and SGA
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	23	664
2013 Realignment Program | Selling General and Administrative Expense
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	23	664	1,361
2013 Realignment Program | Total COGS and SGA
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 23	$ 664	$ 1,361