Goodwill and Other Intangible Assets - Summary of Changes in Quanta's Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill, beginning balance	$ 1,780,717us-gaap_Goodwill	$ 1,537,645us-gaap_Goodwill
Goodwill acquired	174,485us-gaap_GoodwillAcquiredDuringPeriod	255,806us-gaap_GoodwillAcquiredDuringPeriod
Foreign currency translation adjustment related to goodwill	(23,717)us-gaap_GoodwillTranslationAdjustments	(12,734)us-gaap_GoodwillTranslationAdjustments
Goodwill, ending balance	1,931,485us-gaap_Goodwill	1,780,717us-gaap_Goodwill
Electric Power Division [Member]
Goodwill [Line Items]
Goodwill, beginning balance	1,168,084	1,065,152
Goodwill acquired	71,517	112,549
Foreign currency translation adjustment related to goodwill	(16,377)	(9,617)
Goodwill, ending balance	1,223,224	1,168,084
Oil and Gas Infrastructure Division [Member]
Goodwill [Line Items]
Goodwill, beginning balance	277,843	137,703
Goodwill acquired	102,968	143,257
Foreign currency translation adjustment related to goodwill	(7,340)	(3,117)
Goodwill, ending balance	373,471	277,843
Fiber Optic Licensing Division [Member]
Goodwill [Line Items]
Goodwill, beginning balance	334,790	334,790
Goodwill acquired
Foreign currency translation adjustment related to goodwill
Goodwill, ending balance	$ 334,790	$ 334,790

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

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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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://www.xbrl.org/2003/role/presentationRef

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