Business and Organization - Additional Information (Detail) $ in Millions		3 Months Ended		6 Months Ended	12 Months Ended
	Aug. 04, 2015 USD ($)	Mar. 31, 2016 Acquisition	Sep. 30, 2015 USD ($)	Jun. 30, 2016 Segment	Dec. 31, 2015 Entity
Organization And Description Of Business [Line Items]
Number of reportable segments | Segment				2
Acquisitions 2015 [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					11
Acquisitions 2015 [Member] | Electric Power Infrastructure Services Business [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					8
Acquisitions 2015 [Member] | Electric Power Infrastructure Services Business [Member] | United States [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					4
Acquisitions 2015 [Member] | Electric Power Infrastructure Services Business [Member] | Australia [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					1
Acquisitions 2015 [Member] | Electric Power Infrastructure Services Business [Member] | Canada [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					3
Acquisitions 2015 [Member] | Oil and Gas Infrastructure Services Business [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					3
Acquisitions 2015 [Member] | Oil and Gas Infrastructure Services Business [Member] | United States [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					1
Acquisitions 2015 [Member] | Oil and Gas Infrastructure Services Business [Member] | Australia [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					1
Acquisitions 2015 [Member] | Oil and Gas Infrastructure Services Business [Member] | Canada [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions					1
Acquisitions 2016 [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition		3
Acquisitions 2016 [Member] | Electric Power Infrastructure Services Business [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition		2
Acquisitions 2016 [Member] | Electric Power Infrastructure Services Business [Member] | United States [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition		1
Acquisitions 2016 [Member] | Electric Power Infrastructure Services Business [Member] | Canada [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition		1
Acquisitions 2016 [Member] | Oil and Gas Infrastructure Services Business [Member] | United States [Member]
Organization And Description Of Business [Line Items]
Number of business acquisitions | Acquisition		1
Fiber Optic Licensing Division [Member]
Organization And Description Of Business [Line Items]
Sales price of fiber optic licensing operations | $	$ 1,000
Net cash proceeds from sale of fiber optic licensing operations | $	$ 848
Gain on sale, Net of tax | $			$ 171