Restructuring Costs and Other - Summary of Costs (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Total expected costs	$ 27.0
Costs incurred	0.7	$ 20.3
Remaining costs at 6/30/2018	6.0
2018 Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	5.1
Costs incurred	1.3	0.0
Remaining costs at 6/30/2018	3.8
2018 Restructuring Actions | Electrical Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	4.6
Costs incurred	0.8	0.0
Remaining costs at 6/30/2018	3.8
2018 Restructuring Actions | Power Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	0.5
Costs incurred	0.5	0.0
Remaining costs at 6/30/2018	0.0
2017 and Prior Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	21.9
Costs incurred	(0.6)	20.3
Remaining costs at 6/30/2018	2.2
2017 and Prior Restructuring Actions | Electrical Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	18.2
Costs incurred	(0.1)	16.9
Remaining costs at 6/30/2018	1.4
2017 and Prior Restructuring Actions | Power Segment
Restructuring Cost and Reserve [Line Items]
Total expected costs	3.7
Costs incurred	(0.5)	$ 3.4
Remaining costs at 6/30/2018	$ 0.8