Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Schedule 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 nine months ended September 30, 2021 and 2020 is set forth below (shares in thousands):


	2021		2020
	RSUs	Weighted Average Grant Date Fair Value (Per share)	RSUs	Weighted Average Grant Date Fair Value (Per share)
Unvested at January 1	3,869	$37.57	3,265	$35.34
Granted	945	$82.75	2,008	$39.65
Vested	(1,442)	$36.92	(1,228)	$35.68
Forfeited	(119)	$47.23	(114)	$36.26
Unvested at period ended September 30	3,253	$50.71	3,931	$37.41

A summary of the activity for PSUs to be settled in common stock for the nine months ended September 30, 2021 and 2020 is set forth below (shares in thousands):


	2021		2020
	PSUs	Weighted Average Grant Date Fair Value (Per share)	PSUs	Weighted Average Grant Date Fair Value (Per share)
Unvested at January 1	1,047	$37.65	848	$33.20
Granted	174	$90.44	436	$34.59
Vested	(268)	$38.28	(238)	$17.48
Forfeited	(11)	$36.90	—	N/A
Unvested at September 30	942	$47.27	1,046	$37.35

Grant Date Fair Value for Awards of Performance Units Inputs

The Monte Carlo simulation valuation methodology applied the following key inputs:


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