Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Aug. 03, 2016
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Trading Symbol	PWR
Entity Registrant Name	QUANTA SERVICES INC
Entity Central Index Key	0001050915
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		144,194,115
Series F Preferred Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		1
Series G Preferred Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		1
Exchangeable Shares Associated with Series F Preferred Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		3,500,000
Exchangeable Shares Associated with Series G Preferred Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		449,929
Exchangeable Shares Not Associated with Preferred Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		2,926,113