Restructuring (Details) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) employee labor_union	Nov. 10, 2015
Restructuring Cost and Reserve [Line Items]
Finalization of severance agreements, number of labor unions | labor_union								3
Restructuring Reserve [Roll Forward]
Provision	$ 13.3			$ 1.3			$ 13.3	$ 26.9
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	2.3	$ 2.8	$ 6.4	13.2	$ 14.0	$ 29.4	6.4	29.4
Provision	1.4			0.3	7.0	3.3
Cash payments	(0.2)	(0.6)	(3.7)	(4.0)	(7.5)	(19.6)
Translation adjustment	0.1	0.1	0.1	0.2	(0.3)	0.9
Ending Balance	3.6	2.3	2.8	9.7	13.2	14.0	3.6	9.7
Employee Severance [Member] | Drivetrain [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	2.0	2.1	3.7	7.9	11.0	25.3	3.7	25.3
Provision	0.7			0.3	2.4	2.3
Cash payments	(0.2)	(0.2)	(1.6)	(2.7)	(5.3)	(17.3)
Translation adjustment	0.1	0.1	0.0	0.1	(0.2)	0.7
Ending Balance	2.6	2.0	2.1	5.6	7.9	11.0	2.6	5.6
Employee Severance [Member] | Engine [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0.3	0.7	2.7	5.3	3.0	4.1	2.7	4.1
Provision	0.7			0.0	4.6	1.0
Cash payments	0.0	(0.4)	(2.1)	(1.3)	(2.2)	(2.3)
Translation adjustment	0.0	0.0	0.1	0.1	(0.1)	0.2
Ending Balance	1.0	$ 0.3	$ 0.7	4.1	$ 5.3	$ 3.0	1.0	4.1
Sevcon, Inc [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination benefits	0.7
Restructuring Reserve [Roll Forward]
Provision							0.7
Engine [Member]
Restructuring Reserve [Roll Forward]
Provision	$ 12.6						$ 12.6
Remy International Inc.
Restructuring Cost and Reserve [Line Items]
Employee termination benefits				0.3				2.0
Other Restructuring Costs								3.1
Restructuring Reserve [Roll Forward]
Provision				$ 1.3				6.1
Gustav Wahler GmbH u. Co. KG and its general partner
Restructuring Cost and Reserve [Line Items]
Employee termination benefits								4.1
Restructuring Reserve [Roll Forward]
Provision								$ 9.6
Drivetrain [Member]
Restructuring Cost and Reserve [Line Items]
Employee termination costs, number of employees | employee								450
Employee termination benefits								$ 3.0
Other Restructuring Costs								5.2
Restructuring Reserve [Roll Forward]
Provision								$ 8.2
Remy International Inc.
Restructuring Cost and Reserve [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired									100.00%