Business and Organization (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business and Organization
Revenue	$ 480,851	$ 428,760	$ 1,326,850	$ 1,242,240
Percentage of revenue attributable to services			100.00%
Installation of systems in newly constructed facilities
Business and Organization
Percentage of revenue attributable to services			37.00%
Maintenance, repair and replacement services
Business and Organization
Percentage of revenue attributable to services			63.00%
Heating Ventilation Air Conditioning And Plumbing [Member]
Business and Organization
Revenue			$ 1,207,434
Percentage of revenue attributable to services			91.00%
Building Automation Control Systems
Business and Organization
Revenue			$ 66,343
Percentage of revenue attributable to services			5.00%
Other
Business and Organization
Revenue			$ 53,073
Percentage of revenue attributable to services			4.00%