Acquisitions - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Net tangible assets acquired		$ 228,800,000		$ 228,800,000		$ 228,800,000
Identified intangible assets						102,000,000.0
Goodwill acquired						85,500,000
Acquisitions 2021
Business Acquisition [Line Items]
Cash consideration				23,500,000
Value of quanta common stock issued				0
Contingent consideration		0		0		0
Identified intangible assets				9,746,000
Goodwill acquired				12,167,000
Goodwill expected to be deductible for income tax		1,800,000		1,800,000		$ 1,800,000
Revenues included in consolidated results of operations		1,200,000		1,200,000
Income (loss) before taxes		300,000		100,000
Acquisition costs		$ 200,000		$ 400,000
Acquisitions 2021 | Subsequent Event
Business Acquisition [Line Items]
Cash consideration	$ 35,000,000.0
Number of shares granted for acquired companies (in shares)	32,822
Value of quanta common stock issued	$ 2,900,000
Acquisitions 2020
Business Acquisition [Line Items]
Cash consideration							$ 359,575,000
Number of shares granted for acquired companies (in shares)							1,334,469
Value of quanta common stock issued							$ 57,119,000
Aggregate maximum payout amount							$ 6,900,000
Aggregate maximum payout amount, target term							5 years
Contingent consideration							$ 2,250,000
Goodwill acquired							84,161,000
Goodwill expected to be deductible for income tax							$ 72,500,000
Revenues included in consolidated results of operations			$ 5,900,000		$ 7,800,000
Income (loss) before taxes			900,000		0
Acquisition costs			$ 0		$ 800,000