Restructuring Costs - By Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	$ 35.0	$ 23.6	$ 5.1
Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	27.5	15.3	3.4
Selling & administrative expense
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	7.5	8.3	1.7
Operating Segments | Electrical
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	33.9	21.7	5.1
Operating Segments | Electrical | Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	27.3	14.5	3.4
Operating Segments | Electrical | Selling & administrative expense
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	6.6	7.2	$ 1.7
Operating Segments | Power
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	1.1	1.9
Operating Segments | Power | Cost of goods sold
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	0.2	0.8
Operating Segments | Power | Selling & administrative expense
Restructuring Cost and Reserve [Line Items]
Pre-tax restructuring costs	$ 0.9	$ 1.1