Acquisitions (Details) $ in Millions				3 Months Ended			9 Months Ended
	Jun. 30, 2017 item	Apr. 01, 2017 USD ($)	Jan. 01, 2016 USD ($)	Sep. 30, 2017 USD ($) item	Jun. 30, 2017 item	Mar. 31, 2016 item	Sep. 30, 2017 USD ($)
Acquisitions
Number of acquisitions | item				1	3	2
Total purchase price							$ 9.6
Notes to former owners
Acquisitions
Number of acquisitions | item	2
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
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
Revenue in consolidated results							$ 73.2
Purchase price paid in cash		85.7
Promissory note payable		$ 14.3