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Commitments and Contingencies (Concentrations of Credit Risk) - Additional Information (Detail) - Customer Concentration Risk [Member] - Customer | 3 Months Ended | 6 Months Ended | 12 Months Ended
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Jun. 30, 2016 | Jun. 30, 2015 | Jun. 30, 2016 | Jun. 30, 2015 | Dec. 31, 2015
Sales Revenue, Net [Member] |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Number of customers representing ten percent or more of concentration risk | 0 | 0 | 0 | 0 |
Net Position [Member] |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Number of customers representing ten percent or more of concentration risk |  |  | 1 |  | 1
Net Position [Member] | Quanta's Electric Power Infrastructure Services Segment [Member] |  |  |  |  |
Concentration Risk [Line Items] |  |  |  |  |
Number of customers representing ten percent or more of concentration risk |  |  | 1 |  | 1
Concentration risk percentage |  |  | 18.00% |  | 12.00%

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- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6351-108592 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13531-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611 + Details
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