Goodwill and Intangible Assets, net - Changes in Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Roll Forward]
BALANCE DECEMBER 31, 2017	$ 1,089.0
Current year acquisitions (Note 3 – Business Acquisitions)	669.0
Foreign currency translation and prior year acquisitions	2.1
BALANCE MARCH 31, 2018	1,760.1
Electrical
Goodwill [Roll Forward]
BALANCE DECEMBER 31, 2017	717.6
Current year acquisitions (Note 3 – Business Acquisitions)	0.0
Foreign currency translation and prior year acquisitions	1.9
BALANCE MARCH 31, 2018	719.5
Power
Goodwill [Roll Forward]
BALANCE DECEMBER 31, 2017	371.4
Current year acquisitions (Note 3 – Business Acquisitions)	669.0
Foreign currency translation and prior year acquisitions	0.2
BALANCE MARCH 31, 2018	$ 1,040.6