Revenue Recognition - Disaggregation of Revenue From Contracts With Customers (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Net sales		$ 279.8	$ 308.8	$ 836.0	$ 906.9
U.S.
Disaggregation of Revenue [Line Items]
Net sales		219.1	252.6	650.7	705.6
Canada
Disaggregation of Revenue [Line Items]
Net sales		41.6	35.6	113.4	131.2
Europe/Other
Disaggregation of Revenue [Line Items]
Net sales		19.1	20.6	71.9	70.1
Environmental Solutions
Disaggregation of Revenue [Line Items]
Net sales		231.0	254.0	678.2	740.7
Environmental Solutions | Vehicles and equipment
Disaggregation of Revenue [Line Items]
Net sales	[1]	179.1	198.3	531.1	585.7
Environmental Solutions | Parts
Disaggregation of Revenue [Line Items]
Net sales		32.4	34.4	96.7	101.0
Environmental Solutions | Rental income
Disaggregation of Revenue [Line Items]
Net sales	[2]	9.2	12.1	27.3	35.1
Environmental Solutions | Other
Disaggregation of Revenue [Line Items]
Net sales	[3]	10.3	9.2	23.1	18.9
Safety and Security Systems
Disaggregation of Revenue [Line Items]
Net sales		48.8	54.8	157.8	166.2
Safety and Security Systems | Public safety and security equipment
Disaggregation of Revenue [Line Items]
Net sales		29.5	31.6	97.6	98.6
Safety and Security Systems | Industrial signaling equipment
Disaggregation of Revenue [Line Items]
Net sales		11.6	15.1	38.0	45.1
Safety and Security Systems | Warning systems
Disaggregation of Revenue [Line Items]
Net sales		$ 7.7	$ 8.1	$ 22.2	$ 22.5

[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.