Restructuring Costs and Other - Summary of Costs (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Total expected costs	$ 31.3
Costs incurred	3.1	$ 20.3
Remaining costs at 9/30/2018	7.9
2018 Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	11.1
Costs incurred	3.7	0.0
Remaining costs at 9/30/2018	7.4
2018 Restructuring Actions | Electrical Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	6.7
Costs incurred	2.1	0.0
Remaining costs at 9/30/2018	4.6
2018 Restructuring Actions | Power Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	4.4
Costs incurred	1.6	0.0
Remaining costs at 9/30/2018	2.8
2017 and Prior Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	20.2
Costs incurred	(0.6)	20.3
Remaining costs at 9/30/2018	0.5
2017 and Prior Restructuring Actions | Electrical Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	17.2
Costs incurred	0.0	16.9
Remaining costs at 9/30/2018	0.3
2017 and Prior Restructuring Actions | Power Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	3.0
Costs incurred	(0.6)	$ 3.4
Remaining costs at 9/30/2018	$ 0.2