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

Quarterly report pursuant to Section 13 or 15(d)

Acquisitions - Additional Information (Detail)

Acquisitions - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
Acquisitions - Additional Information (Detail) (USD $)	Mar. 31, 2015 Entity	Mar. 31, 2014	Dec. 31, 2014 Entity
Business Acquisition [Line Items]
Cash paid for acquisitions	$ 36,900,000		$ 284,300,000
Number of business acquisitions	3us-gaap_NumberOfBusinessesAcquired		9us-gaap_NumberOfBusinessesAcquired
Number of shares granted for acquired companies			686,382
Value of equity interests transferred			134,500,000
Goodwill acquired	18,331,000us-gaap_GoodwillAcquiredDuringPeriod
Fair value of accounts receivable acquired	6,200,000		117,000,000
Goodwill expected to be deductible for income tax	0		30,100,000
Income (loss) from continuing operations before income taxes	92,560,000	91,701,000
Third and Fourth Quarter 2014 [Member]
Business Acquisition [Line Items]
Net tangible assets acquired			106,900,000
Goodwill acquired			116,100,000
Other intangible assets, acquired			73,900,000
Contributed by Acquisitions [Member]
Business Acquisition [Line Items]
Revenues	7,000,000
Income (loss) from continuing operations before income taxes	(1,000,000)
Acquisition costs	500,000
First Quarter Two Thousand Fifteen [Member]
Business Acquisition [Line Items]
Net tangible assets acquired	9,500,000
Goodwill acquired	18,300,000
Other intangible assets, acquired	9,100,000
Canadian Subsidiaries [Member] \| Exchangeable Shares [Member]
Business Acquisition [Line Items]
Number of shares granted for acquired companies			3,825,971
Series G Preferred Stock [Member]
Business Acquisition [Line Items]
Number of shares granted for acquired companies			1
Series G Preferred Stock [Member] \| Canadian Subsidiaries [Member] \| Exchangeable Shares [Member]
Business Acquisition [Line Items]
Number of shares granted for acquired companies			899,858
Oil and Gas Infrastructure Services Business [Member] \| Canada [Member]
Business Acquisition [Line Items]
Number of business acquisitions	1		2
Oil and Gas Infrastructure Services Business [Member] \| Australia [Member]
Business Acquisition [Line Items]
Number of business acquisitions	1
Oil and Gas Infrastructure Services Business [Member] \| United States [Member]
Business Acquisition [Line Items]
Number of business acquisitions			1
Electric Power Infrastructure Services Business [Member] \| Canada [Member]
Business Acquisition [Line Items]
Number of business acquisitions	1		4
Electric Power Infrastructure Services Business [Member] \| Australia [Member]
Business Acquisition [Line Items]
Number of business acquisitions			1
Electric Power Infrastructure Services Business [Member] \| United States [Member]
Business Acquisition [Line Items]
Number of business acquisitions			1
Electric Power Division [Member]
Business Acquisition [Line Items]
Goodwill acquired	949,000		71,500,000
Oil and Gas Infrastructure Division [Member]
Business Acquisition [Line Items]
Goodwill acquired	$ 17,382,000		$ 103,000,000