Revenue Recognition - Disaggregation of Revenue From Contracts With Customers (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net sales		$ 298.3	$ 279.8	$ 911.8	$ 836.0
U.S.
Disaggregation of Revenue [Line Items]
Net sales		233.3	219.1	692.5	650.7
Canada
Disaggregation of Revenue [Line Items]
Net sales		44.9	41.6	151.6	113.4
Europe/Other
Disaggregation of Revenue [Line Items]
Net sales		20.1	19.1	67.7	71.9
Environmental Solutions
Disaggregation of Revenue [Line Items]
Net sales		249.1	231.0	758.5	678.2
Environmental Solutions | Vehicles and equipment
Disaggregation of Revenue [Line Items]
Net sales	[1]	185.5	179.1	578.2	531.1
Environmental Solutions | Parts
Disaggregation of Revenue [Line Items]
Net sales		37.5	32.4	112.7	96.7
Environmental Solutions | Rental income
Disaggregation of Revenue [Line Items]
Net sales	[2]	11.9	9.2	32.6	27.3
Environmental Solutions | Other
Disaggregation of Revenue [Line Items]
Net sales	[3]	14.2	10.3	35.0	23.1
Safety and Security Systems
Disaggregation of Revenue [Line Items]
Net sales		49.2	48.8	153.3	157.8
Safety and Security Systems | Public safety and security equipment
Disaggregation of Revenue [Line Items]
Net sales		30.2	29.5	93.6	97.6
Safety and Security Systems | Industrial signaling equipment
Disaggregation of Revenue [Line Items]
Net sales		12.2	11.6	39.9	38.0
Safety and Security Systems | Warning systems
Disaggregation of Revenue [Line Items]
Net sales		$ 6.8	$ 7.7	$ 19.8	$ 22.2

[1] Includes net sales from the sale of new and used vehicles and equipment, including sales of rental equipment.

[2] Represents income from vehicle and equipment lease arrangements with customers.

[3] Primarily includes revenues from services, such as maintenance and repair work, and the sale of extended warranty contracts.