Goodwill and Other Intangible Assets - Summary of Changes in Quanta's Goodwill (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($)
Goodwill [Line Items]
Goodwill gross, beginning balance	$ 1,642,902
Accumulated impairment, beginning balance	(39,733)
Goodwill, beginning balance	1,603,169
Purchase price allocation adjustments	(659)
Foreign currency translation adjustments	5,874
Goodwill gross, ending balance	1,648,884
Accumulated impairment, ending balance	(40,500)
Goodwill, ending balance	1,608,384
Electric Power Division [Member]
Goodwill [Line Items]
Goodwill gross, beginning balance	1,253,979
Accumulated impairment, beginning balance	0
Goodwill, beginning balance	1,253,979
Purchase price allocation adjustments	0
Foreign currency translation adjustments	3,354
Goodwill gross, ending balance	1,257,333
Accumulated impairment, ending balance	0
Goodwill, ending balance	1,257,333
Oil and Gas Infrastructure Division [Member]
Goodwill [Line Items]
Goodwill gross, beginning balance	388,923
Accumulated impairment, beginning balance	(39,733)
Goodwill, beginning balance	349,190
Purchase price allocation adjustments	(659)
Foreign currency translation adjustments	2,520
Goodwill gross, ending balance	391,551
Accumulated impairment, ending balance	(40,500)
Goodwill, ending balance	$ 351,051

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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e961-128460

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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