Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of RSUs and PSUs to be Settled in Common Stock Activity

A summary of the activity for RSUs to be settled in common stock for the years ended December 31, 2021, 2020 and 2019 is as follows (shares in thousands):

	2021		2020		2019
	Shares	Weighted Average Grant Date Fair Value (Per share)	Shares	Weighted Average Grant Date Fair Value (Per share)	Shares	Weighted Average Grant Date Fair Value (Per share)
Unvested at January 1	3,869	$37.57	3,265	$35.34	2,634	$33.50
Granted	1,642	$94.83	2,029	$39.91	2,142	$35.62
Vested	(1,476)	$37.03	(1,269)	$35.69	(1,349)	$32.22
Forfeited	(155)	$48.52	(156)	$36.67	(162)	$35.20
Unvested at December 31	3,880	$61.64	3,869	$37.57	3,265	$35.34

A summary of the activity for PSUs to be settled in common stock for the years ended December 31, 2021, 2020 and 2019 is as follows (shares in thousands):

	2021		2020		2019
	Shares	Weighted Average Grant Date Fair Value (Per share)	Shares	Weighted Average Grant Date Fair Value (Per share) (1)	Shares	Weighted Average Grant Date Fair Value (Per share)
Unvested at January 1	1,047	$37.65	848	$40.04	775	$34.72
Granted	174	$90.44	437	$34.60	358	$40.15
Vested	(268)	$38.28	(238)	$41.87	(236)	$22.73
Forfeited	(22)	$41.86	—	N/A	(49)	$40.07
Unvested at December 31	931	$47.27	1,047	$37.65	848	$40.04

(1) Certain weighted average grant date fair value per share amounts related to the year ended December 31, 2020 have been recast to conform to the correction of the valuation of PSUs described below.

Grant Date Fair Value for Awards of Performance Units Inputs

The grant date fair values of the PSUs were determined as follows: (i) for the portion of the awards based on company financial and operational performance metrics, by utilizing the closing price of Quanta’s common stock on the date of grant and (ii) for the portion of the awards based on total shareholder return, by utilizing a Monte Carlo simulation valuation methodology. The Monte Carlo simulation valuation methodology applied the following key inputs:

	2021		2020		2019
Valuation date price based on March 25, 2021, March 26, 2020 and March 8, 2019 closing stock prices of Quanta common stock	$83.48		$31.49		$35.19
Expected volatility	36	%	34	%	25	%
Risk-free interest rate	0.26	%	0.35	%	2.43	%
Term in years	2.77		2.76		2.81