Restructuring Costs and Other - Summary of Costs (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Total expected costs	$ 55.3			$ 55.3
Costs incurred				13.5		$ 35.0
Remaining costs at 9/30/2017	6.8			6.8
Restructuring charges	3.3		$ 4.5	13.5	$ 13.9
Electrical
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2.8		4.3	11.5	12.8
Power
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.5		$ 0.2	2.0	$ 1.1
2017 Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	12.1			12.1
Costs incurred				8.4		0.0
Remaining costs at 9/30/2017	3.7			3.7
Restructuring charges				8.4
2017 Restructuring Actions | Withdrawal from Multiemployer Defined Benefit Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 12.5
2017 Restructuring Actions | Electrical
Restructuring Cost and Reserve [Line Items]
Total expected costs	8.4			8.4
Costs incurred				6.4		0.0
Remaining costs at 9/30/2017	2.0			2.0
2017 Restructuring Actions | Electrical | Withdrawal from Multiemployer Defined Benefit Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 12.5
2017 Restructuring Actions | Power
Restructuring Cost and Reserve [Line Items]
Total expected costs	3.7			3.7
Costs incurred				2.0		0.0
Remaining costs at 9/30/2017	1.7			1.7
2016 and Prior Restructuring Actions
Restructuring Cost and Reserve [Line Items]
Total expected costs	43.2			43.2
Costs incurred				5.1		35.0
Remaining costs at 9/30/2017	3.1			3.1
Restructuring charges				5.1
2016 and Prior Restructuring Actions | Electrical
Restructuring Cost and Reserve [Line Items]
Total expected costs	41.8			41.8
Costs incurred				5.1		33.9
Remaining costs at 9/30/2017	2.8			2.8
2016 and Prior Restructuring Actions | Power
Restructuring Cost and Reserve [Line Items]
Total expected costs	1.4			1.4
Costs incurred				0.0		$ 1.1
Remaining costs at 9/30/2017	$ 0.3			$ 0.3