Restructuring (Details) $ in Millions	3 Months Ended						12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2018 USD ($) employee	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) employee labor_union	Sep. 27, 2017	Nov. 10, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Agreements with Labor Unions, Number | labor_union									3
Restructuring Reserve [Roll Forward]
Provision	$ 22.7	$ 5.7	$ 31.2	$ 7.5	$ 45.2	$ 13.3	$ 67.1	$ 58.5	$ 26.9
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				5.4			5.4	6.4
Provision							41.5	6.1
Cash payments							(21.8)	(7.5)
Translation adjustment							(0.4)	0.4
Restructuring reserve, ending balance	24.7				5.4		24.7	5.4	6.4
Sevcon, Inc [Member]
Restructuring Cost and Reserve [Line Items]
Business acquisition, percentage of voting interests acquired										100.00%
Gustav Wahler GmbH u. Co. KG and General Partner [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination benefits									9.6
Remy International Inc. [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination benefits									2.0
Other restructuring charges									3.1
Business acquisition, percentage of voting interests acquired											100.00%
Restructuring Reserve [Roll Forward]
Provision									6.1
Engine [Member]
Restructuring Reserve [Roll Forward]
Provision							$ 53.5	48.2
Engine [Member] | Emissions [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination benefits, number of employees effected | employee							140
Engine [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				1.3			$ 1.3	2.7
Provision							34.4	1.4
Cash payments							(14.5)	(2.9)
Translation adjustment							(0.4)	0.1
Restructuring reserve, ending balance	20.8				1.3		20.8	1.3	$ 2.7
Engine [Member] | Employee Severance [Member] | Emissions [Member]
Restructuring Reserve [Roll Forward]
Provision							28.4
Engine [Member] | Employee Severance [Member] | Non-Emissions [Member]
Restructuring Reserve [Roll Forward]
Provision							6.0
Drivetrain [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination benefits, number of employees effected | employee									450
Employee termination benefits									$ 3.0
Other restructuring charges									5.2
Restructuring Reserve [Roll Forward]
Provision							10.3	6.8	8.2
Drivetrain [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				$ 4.1			4.1	3.7
Provision							7.1	4.7
Cash payments							(7.3)	(4.6)
Translation adjustment							0.0	0.3
Restructuring reserve, ending balance	$ 3.9				$ 4.1		$ 3.9	$ 4.1	$ 3.7