Segment Information - Summary of Net Sales, Operating Income (Loss), and Total Assets by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total net sales	$ 269.4	$ 248.7	$ 810.1	$ 650.9
Total operating income	30.4	22.3	88.1	52.5
Interest expense	2.2	2.7	7.2	4.6
Other (income) expense, net	0.0	(0.4)	0.5	(0.7)
Income before income taxes	28.2	20.0	80.4	48.6
Total assets	1,009.3		1,009.3		$ 992.3
Continuing Operations
Segment Reporting Information [Line Items]
Total assets	1,008.8		1,008.8		991.8
Discontinued Operations
Segment Reporting Information [Line Items]
Total assets	0.5		0.5		0.5
Environmental Solutions
Segment Reporting Information [Line Items]
Total net sales	216.3	198.5	646.2	500.6
Total operating income	28.3	21.2	86.1	52.5
Environmental Solutions | Continuing Operations
Segment Reporting Information [Line Items]
Total assets	772.8		772.8		746.4
Safety and Security Systems
Segment Reporting Information [Line Items]
Total net sales	53.1	50.2	163.9	150.3
Total operating income	8.0	6.1	22.3	18.1
Safety and Security Systems | Continuing Operations
Segment Reporting Information [Line Items]
Total assets	210.4		210.4		211.8
Corporate And Eliminations
Segment Reporting Information [Line Items]
Total operating income	(5.9)	$ (5.0)	(20.3)	$ (18.1)
Corporate And Eliminations | Continuing Operations
Segment Reporting Information [Line Items]
Total assets	$ 25.6		$ 25.6		$ 33.6