Nature of Operations and Basis of Presentation - Schedule of Goodwill (Detail) - Jun. 30, 2015 - USD ($)	Total	Total
Goodwill [Line Items]
Goodwill, Beginning balance		$ 143,160,000
Acquisition date adjustment	$ 0	1,380,000
Foreign currency translation adjustment		(6,283,000)
Goodwill, Ending balance	138,257,000	138,257,000
Natural Gas Operations [Member]
Goodwill [Line Items]
Goodwill, Beginning balance		10,095,000
Acquisition date adjustment		0
Foreign currency translation adjustment		0
Goodwill, Ending balance	10,095,000	10,095,000
Construction Services [Member]
Goodwill [Line Items]
Goodwill, Beginning balance		133,065,000
Acquisition date adjustment		1,380,000
Foreign currency translation adjustment		(6,283,000)
Goodwill, Ending balance	$ 128,162,000	$ 128,162,000