Segment Information - Summary of Net Sales, Operating Income (Loss), and Total Assets by Segment (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total net sales	$ 172.3	$ 205.4	$ 345.1	$ 401.9
Total operating income	14.3	29.2	30.4	53.7
Interest expense	0.4	0.6	0.8	1.2
Debt settlement charges	0.0	0.0	0.3	0.0
Other (income) expense, net	(0.3)	0.0	(1.0)	1.2
Income before income taxes	14.2	28.6	30.3	51.3
Total assets	651.3		651.3		$ 666.5
Continuing Operations
Segment Reporting Information [Line Items]
Total assets	648.9		648.9		559.4
Discontinued Operations
Segment Reporting Information [Line Items]
Total assets	2.4		2.4		107.1
Corporate and Eliminations
Segment Reporting Information [Line Items]
Total operating income	(7.2)	(7.3)	(12.5)	(13.3)
Corporate and Eliminations | Continuing Operations
Segment Reporting Information [Line Items]
Total assets	44.5		44.5		99.2
Environmental Solutions | Operating Segments
Segment Reporting Information [Line Items]
Total net sales	119.4	146.6	234.8	286.8
Total operating income	14.9	29.2	31.4	53.1
Environmental Solutions | Operating Segments | Continuing Operations
Segment Reporting Information [Line Items]
Total assets	396.1		396.1		250.6
Safety And Security Systems | Operating Segments
Segment Reporting Information [Line Items]
Total net sales	52.9	58.8	110.3	115.1
Total operating income	6.6	$ 7.3	11.5	$ 13.9
Safety And Security Systems | Operating Segments | Continuing Operations
Segment Reporting Information [Line Items]
Total assets	$ 208.3		$ 208.3		$ 209.6