Restructuring Costs and Other - Summary of Costs (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Total expected costs	$ 27.8
Costs incurred	0.7	$ 20.3
Remaining costs at 3/31/2018	6.8
2018 Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	4.3
Costs incurred	0.3	0.0
Remaining costs at 3/31/2018	4.0
2018 Restructuring Actions | Electrical Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	4.2
Costs incurred	0.2	0.0
Remaining costs at 3/31/2018	4.0
2018 Restructuring Actions | Power Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	0.1
Costs incurred	0.1	0.0
Remaining costs at 3/31/2018	0.0
2017 and Prior Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	23.5
Costs incurred	0.4	20.3
Remaining costs at 3/31/2018	2.8
2017 and Prior Restructuring Actions | Electrical Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	19.7
Costs incurred	0.5	16.9
Remaining costs at 3/31/2018	2.3
2017 and Prior Restructuring Actions | Power Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	3.8
Costs incurred	(0.1)	$ 3.4
Remaining costs at 3/31/2018	$ 0.5