Stock-Based Compensation - RSUs to be Settled in Cash (Details) - Restricted Stock Units to be Settled in Cash - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares that may be received by RSU holder (in shares)	1
Compensation expense related to RSUs to be settled in cash	$ 5.9	$ 5.0	$ 8.1
Payments to settle liabilities under compensation plan	5.4	5.9	$ 8.6
Accrued liabilities under compensation plan	$ 4.3	$ 3.4

Amount in cash received for each RSU is equal to the fair value of this number of Quanta common stock shares.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements payable within one year (or the operating cycle, if longer).

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Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.

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