Acquisitions (Details) $ in Millions				3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) item	Apr. 01, 2017 USD ($)	Jan. 01, 2016 USD ($)	Jun. 30, 2017 USD ($) item	Mar. 31, 2016 item	Jun. 30, 2017 USD ($)
Acquisitions
Number of acquisitions | item				3	2
Total purchase price						$ 7.8
Notes to former owners
Acquisitions
Number of acquisitions | item	3
Environmental Air Systems
Acquisitions
Interest acquired (as a percent)			40.00%
Total purchase price			$ 46.6
Purchase price paid in cash			$ 42.0
Shoffner
Acquisitions
Interest acquired (as a percent)					100.00%
Total purchase price						19.8
Amount allocated to goodwill and identifiable intangible assets for acquisitions	$ 14.8			$ 14.8		14.8
Purchase price paid in cash						15.5
BCH
Acquisitions
Total purchase price		$ 100.0				122.6
Amount allocated to goodwill and identifiable intangible assets for acquisitions	$ 97.9			$ 97.9		97.9
Revenue in consolidated results						$ 38.6
Purchase price paid in cash		85.7
Promissory note payable		$ 14.3