Revenue Recognition - Disaggregation of Revenue From Contracts With Customers (Details) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2018	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Net sales		$ 291.0	$ 540.7
U.S.
Disaggregation of Revenue [Line Items]
Net sales		220.7	417.3
Canada
Disaggregation of Revenue [Line Items]
Net sales		45.8	78.2
Europe/Other
Disaggregation of Revenue [Line Items]
Net sales		24.5	45.2
Environmental Solutions
Disaggregation of Revenue [Line Items]
Net sales		233.3	429.9
Environmental Solutions | Vehicles and equipment
Disaggregation of Revenue [Line Items]
Net sales	[1]	185.2	340.8
Environmental Solutions | Parts
Disaggregation of Revenue [Line Items]
Net sales		32.4	62.2
Environmental Solutions | Rental income
Disaggregation of Revenue [Line Items]
Net sales	[2]	11.6	19.4
Environmental Solutions | Other
Disaggregation of Revenue [Line Items]
Net sales	[3]	4.1	7.5
Safety and Security Systems
Disaggregation of Revenue [Line Items]
Net sales		57.7	110.8
Safety and Security Systems | Public safety and security equipment
Disaggregation of Revenue [Line Items]
Net sales		36.7	67.3
Safety and Security Systems | Industrial signaling equipment
Disaggregation of Revenue [Line Items]
Net sales		13.5	26.7
Safety and Security Systems | Warning systems
Disaggregation of Revenue [Line Items]
Net sales		$ 7.5	$ 16.8

[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, recognized in accordance with Topic 840.

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