Quanta Services, Inc. Quarterly report pursuant to Section 13 or 15(d)

Acquisition - Estimated Fair Values of Identifiable Intangible Assets and Related Weighted Average Amortization (Detail) (Acquisitions [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 9,068
Weighted Average Amortization Period at Acquisition Date	13 years 3 months 18 days
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	6,391
Weighted Average Amortization Period at Acquisition Date	17 years 2 months 12 days
Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	741
Weighted Average Amortization Period at Acquisition Date	6 months
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	1,408
Weighted Average Amortization Period at Acquisition Date	5 years
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated Fair Value at Acquisition Date	$ 528
Weighted Average Amortization Period at Acquisition Date	5 years