Quarterly report pursuant to Section 13 or 15(d)

Goodwill and Other Intangible Assets - Summary of Changes in Quanta's Goodwill (Detail)

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Goodwill and Other Intangible Assets - Summary of Changes in Quanta's Goodwill (Detail) - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Jun. 30, 2018
Jun. 30, 2018
Goodwill [Roll Forward]    
Goodwill gross, beginning balance $ 1,966,432  
Accumulated impairment, beginning balance (97,832)  
Goodwill, beginning balance 1,868,600  
Goodwill acquired 43,181 $ 344,200
Purchase price allocation adjustments 51  
Foreign currency translation adjustments (14,168)  
Goodwill gross, ending balance 1,994,776 1,994,776
Accumulated impairment, ending balance (97,112) (97,112)
Goodwill, ending balance 1,897,664 1,897,664
Electric Power Infrastructure Services Division    
Goodwill [Roll Forward]    
Goodwill gross, beginning balance 1,272,527  
Accumulated impairment, beginning balance 0  
Goodwill, beginning balance 1,272,527  
Goodwill acquired 43,181  
Purchase price allocation adjustments 51  
Foreign currency translation adjustments (8,772)  
Goodwill gross, ending balance 1,306,987 1,306,987
Accumulated impairment, ending balance 0 0
Goodwill, ending balance 1,306,987 1,306,987
Oil and Gas Infrastructure Services Division    
Goodwill [Roll Forward]    
Goodwill gross, beginning balance 693,905  
Accumulated impairment, beginning balance (97,832)  
Goodwill, beginning balance 596,073  
Goodwill acquired 0  
Purchase price allocation adjustments 0  
Foreign currency translation adjustments (5,396)  
Goodwill gross, ending balance 687,789 687,789
Accumulated impairment, ending balance (97,112) (97,112)
Goodwill, ending balance $ 590,677 $ 590,677