Business Acquisitions - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired			$ 172,500,000	$ 163,300,000
Goodwill	$ 992,000,000		992,000,000		$ 928,500,000
R.W. Lyall & Company, Inc.
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 129,100,000
Intangible assets		68,900,000
Goodwill		$ 48,400,000
Intangible assets, useful life		21 years
EMC
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired		$ 42,500,000
Intangible assets		16,900,000
Goodwill		16,400,000
Goodwill, expected to be tax deductible		$ 0
Intangible assets, useful life		19 years
Jiangsu Xiangyuan Electrical Equipment Co., Ltd. (Longbow)
Business Acquisition [Line Items]
Acquisition of businesses, net of cash acquired	2,900,000
Intangible assets	6,800,000		6,800,000
Goodwill	2,000,000		2,000,000
Payments to acquire business	14,200,000
Deferred payments to acquire business	13,300,000		$ 13,300,000
Cash received	$ 2,000,000
Intangible assets, useful life	11 years