Nature of Operations and Basis of Presentation - Schedule of Goodwill (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill, Beginning balance	$ 179,314
Foreign currency translation adjustment	(3,437)
Goodwill, Ending balance	176,059
Neuco
Goodwill [Roll Forward]
Additional goodwill from Neuco acquisition	182
Natural Gas Operations
Goodwill [Roll Forward]
Goodwill, Beginning balance	10,095
Additional goodwill from Neuco acquisition	0
Foreign currency translation adjustment	0
Goodwill, Ending balance	10,095
Infrastructure Services
Goodwill [Roll Forward]
Goodwill, Beginning balance	169,219
Foreign currency translation adjustment	(3,437)
Goodwill, Ending balance	165,964
Infrastructure Services \| Neuco
Goodwill [Roll Forward]
Additional goodwill from Neuco acquisition	$ 182

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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