Acquisitions - Narrative (Details) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 13, 2021 USD ($) shares	Jul. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($) Businesses shares
Business Acquisition [Line Items]
Total contingent consideration liabilities			$ 148,150		$ 148,150		$ 148,150	$ 143,073
Net tangible assets acquired							230,700
Intangible assets							1,520,000
Goodwill							1,460,000
Purchase price allocation adjustments					64,900
Goodwill expected to be deductible for income tax								1,490,000
Construction Contracting Services Business Acquisition
Business Acquisition [Line Items]
Cash consideration		$ 22,000
Contingent consideration payments (up to)		$ 15,000
Post-acquisition period, financial performance objectives		5 years
Total contingent consideration liabilities			2,600		2,600		2,600
Value of Quanta common stock issued					0
Cash consideration					21,990
Intangible assets					13,109
Goodwill					12,225
Goodwill expected to be deductible for income tax			12,200		12,200		12,200
Revenues included in consolidated results of operations			5,100		5,100
Income (loss) before taxes			200		200
Acquisition costs			600		600
Blattner Holding Company
Business Acquisition [Line Items]
Cash consideration	$ 2,430,000
Contingent consideration payments (up to)	$ 300,000
Post-acquisition period, financial performance objectives	3 years
Total contingent consideration liabilities	$ 125,600		134,500		134,500		134,500	125,632
Number of shares granted for acquired companies (in shares) | shares	3,326,955
Value of Quanta common stock issued	$ 345,400							345,422
Post-acquisition period, deferred earnings, accrued interest	5.00%
Cash consideration								2,434,877
Intangible assets								1,425,000
Goodwill								$ 1,364,155
Businesses That Provide Electric Power Construction Services In The United States
Business Acquisition [Line Items]
Number of businesses acquired | Businesses								3
Acquisitions In 2021 Excluding Blattner
Business Acquisition [Line Items]
Total contingent consideration liabilities								$ 0
Number of shares granted for acquired companies (in shares) | shares								187,093
Value of Quanta common stock issued								$ 16,922
Cash consideration								328,375
Intangible assets								104,143
Goodwill								$ 113,948
All Acquisitions
Business Acquisition [Line Items]
Contingent consideration payments (up to)			$ 327,000		$ 327,000		$ 327,000
Acquisitions 2021
Business Acquisition [Line Items]
Revenues included in consolidated results of operations				$ 55,200		$ 63,000
Income (loss) before taxes				1,000		1,000
Acquisition costs				$ 10,600		$ 11,400