Goodwill and Other Intangible Assets - Summary of Changes in Quanta's Goodwill (Detail) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Goodwill [Line Items]
Goodwill gross, beginning balance	$ 1,592,551
Goodwill, beginning balance	1,552,658
Goodwill acquired	26,116	$ 51,641
Purchase price allocation adjustments	(214)
Foreign currency translation adjustments	16,995
Goodwill gross, ending balance	1,635,740	1,592,551
Accumulated impairment	(40,185)	(39,893)
Goodwill, ending balance	1,595,555	1,552,658
Electric Power Division [Member]
Goodwill [Line Items]
Goodwill gross, beginning balance	1,226,245
Goodwill, beginning balance	1,226,245
Goodwill acquired	5,829
Foreign currency translation adjustments	10,702
Goodwill gross, ending balance	1,242,776	1,226,245
Goodwill, ending balance	1,242,776	1,226,245
Oil and Gas Infrastructure Division [Member]
Goodwill [Line Items]
Goodwill gross, beginning balance	366,306
Goodwill, beginning balance	326,413
Goodwill acquired	20,287
Purchase price allocation adjustments	(214)
Foreign currency translation adjustments	6,293
Goodwill gross, ending balance	392,964	366,306
Accumulated impairment	(40,185)	(39,893)
Goodwill, ending balance	$ 352,779	$ 326,413

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
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-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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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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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

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