Debt Obligations - Senior Credit Facility (Details)						12 Months Ended
	Oct. 13, 2021 USD ($)	Oct. 08, 2021 USD ($)	Oct. 07, 2021	Sep. 30, 2020	Sep. 21, 2020	Dec. 31, 2021 USD ($) unit	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 22, 2020 USD ($)
Line of Credit Facility [Line Items]
Payments under credit facility						$ 4,265,478,000	$ 4,187,645,000	$ 5,903,069,000
Borrowings under senior credit facility						1,199,841,000	148,508,000
Borrowings under credit facility						5,316,002,000	2,983,529,000	6,175,558,000
Debt issuance costs related to amendment						12,568,000	11,089,000	2,309,000
Amortization expense related to capitalized debt issuance costs						8,405,000	5,126,000	$ 1,870,000
Term Loan
Line of Credit Facility [Line Items]
Payments under credit facility							1,210,000,000
Senior Credit Facility
Line of Credit Facility [Line Items]
Option to increase revolving commitments under the credit agreement									$ 400,000,000
Credit facility available for revolving loans or issuing new letters of credit						1,870,000,000
Reduction in Quanta's funded indebtedness reduced by cash and cash equivalents in excess of this amount						25,000,000
Senior Credit Facility | Canadian Dollars
Line of Credit Facility [Line Items]
Borrowings under senior credit facility						312,600,000
Senior Credit Facility | U.S. Dollars
Line of Credit Facility [Line Items]
Borrowings under senior credit facility						102,400,000
Senior Credit Facility | Australian Dollars
Line of Credit Facility [Line Items]
Borrowings under senior credit facility						34,800,000
Senior Credit Facility | Minimum
Line of Credit Facility [Line Items]
Commitment fee				0.275%	0.20%
Senior Credit Facility | Maximum
Line of Credit Facility [Line Items]
Commitment fee				0.425%	0.40%
Senior Credit Facility | Excess of Eurocurrency Rate Applicable to Domestic Borrowings Only | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			1.125%
Senior Credit Facility | Excess of Eurocurrency Rate Applicable to Domestic Borrowings Only | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			2.00%
Senior Credit Facility | Excess of Base Rate Domestic Borrowings Only | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			0.125%
Senior Credit Facility | Excess of Base Rate Domestic Borrowings Only | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			1.00%
Senior Credit Facility | Excess of Euro Currency Rate of Credit Agreement for Foreign Borrowings | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			1.125%
Senior Credit Facility | Excess of Euro Currency Rate of Credit Agreement for Foreign Borrowings | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			2.00%
Senior Credit Facility | Excess of Federal Funds Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			0.50%
Senior Credit Facility | Excess of Euro Currency Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			1.00%
Senior Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Cross default provisions with debt instruments exceeding this amount		$ 300,000,000
Borrowings under senior credit facility						$ 449,800,000
Maximum consolidated leverage ratio						3.5
Acquisition threshold for leverage ratio						$ 200,000,000
Maximum consolidated leverage ratio permissible under credit agreement						4.0
Minimum consolidated interest coverage ratio						3.0
Amount of availability under the credit agreement and/or cash and cash equivalents on hand that must be present to allow for cash payments of dividends and stock repurchases						$ 100,000,000
Deferred financing costs						$ 10,100,000	$ 9,700,000
Debt Instrument, Covenant, Number Of Fiscal Quarters Applicable To Updated Acquisition Ratio | unit						4
Senior Credit Facility | Line of Credit | Minimum
Line of Credit Facility [Line Items]
Commitment fee		0.10%
Senior Credit Facility | Line of Credit | Maximum
Line of Credit Facility [Line Items]
Commitment fee		0.275%
Senior Credit Facility | Revolving Credit Facility | Line of Credit
Line of Credit Facility [Line Items]
Senior secured revolving credit facility		$ 2,640,000,000
Borrowed amount	$ 50,900,000
Senior Credit Facility | Revolving Credit Facility | Line of Credit | London Interbank Offered Rate (LIBOR) | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.125%
Senior Credit Facility | Revolving Credit Facility | Line of Credit | London Interbank Offered Rate (LIBOR) | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.75%
Senior Credit Facility | Revolving Credit Facility | Line of Credit | Alternative Currency Term Rate | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.125%
Senior Credit Facility | Revolving Credit Facility | Line of Credit | Alternative Currency Term Rate | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.75%
Senior Credit Facility | Revolving Credit Facility | Line of Credit | Base Rate | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		0.125%
Senior Credit Facility | Revolving Credit Facility | Line of Credit | Base Rate | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		0.75%
Senior Credit Facility | Standby Letters of Credit | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			1.125%
Senior Credit Facility | Standby Letters of Credit | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			2.00%
Senior Credit Facility | Standby Letters of Credit | Line of Credit | Minimum
Line of Credit Facility [Line Items]
Letter of credit fee		1.125%
Senior Credit Facility | Standby Letters of Credit | Line of Credit | Maximum
Line of Credit Facility [Line Items]
Letter of credit fee		1.75%
Senior Credit Facility | Performance Letters of Credit | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			0.675%
Senior Credit Facility | Performance Letters of Credit | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate			1.15%
Senior Credit Facility | Performance Letters of Credit | Line of Credit | Minimum
Line of Credit Facility [Line Items]
Letter of credit fee		0.675%
Senior Credit Facility | Performance Letters of Credit | Line of Credit | Maximum
Line of Credit Facility [Line Items]
Letter of credit fee		1.125%
Senior Credit Facility | Letters of Credit
Line of Credit Facility [Line Items]
Letters of credit and bank guarantees under the credit facility						$ 318,200,000
Senior Credit Facility | Letters of Credit and Bank Guarantees | Canadian Dollars
Line of Credit Facility [Line Items]
Letters of credit and bank guarantees under the credit facility						76,500,000
Senior Credit Facility | Letters of Credit and Bank Guarantees | U.S. Dollars
Line of Credit Facility [Line Items]
Letters of credit and bank guarantees under the credit facility						$ 241,700,000
Senior Credit Facility | Term Loan | Payments Due First Business Day Of Quarter In 2023 And 2024
Line of Credit Facility [Line Items]
Quarterly principal payments		$ 4,700,000
Senior Credit Facility | Term Loan | Payments Due First Business Day Of Quarter In 2025
Line of Credit Facility [Line Items]
Quarterly principal payments		9,400,000
Senior Credit Facility | Term Loan | Payments Due First Business Day Of Quarter In 2026
Line of Credit Facility [Line Items]
Quarterly principal payments		18,800,000
Senior Credit Facility | Term Loan | Line of Credit
Line of Credit Facility [Line Items]
Senior secured revolving credit facility		$ 750,000,000
Borrowed amount	$ 750,000,000
Senior Credit Facility | Term Loan | Line of Credit | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.00%
Senior Credit Facility | Term Loan | Line of Credit | London Interbank Offered Rate (LIBOR) | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.00%
Senior Credit Facility | Term Loan | Line of Credit | London Interbank Offered Rate (LIBOR) | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		1.625%
Senior Credit Facility | Term Loan | Line of Credit | Base Rate | Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		0.00%
Senior Credit Facility | Term Loan | Line of Credit | Base Rate | Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		0.625%
Senior Credit Facility | Term Loan | Line of Credit | Fed Funds Effective Rate Overnight Index Swap Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate		0.50%