Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Restricted Stock and RSU to be Settled in Common Stock Activity

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

	Shares		Weighted Average Grant Date Fair Value (Per share)
Unvested at December 31, 2018	2,634		$33.50
Granted	2,142		$35.62
Vested	(1,349	)	$32.22
Forfeited	(162	)	$35.20
Unvested at December 31, 2019	3,265		$35.34

Grant Date Fair Value for Awards of Performance Units Inputs

The grant date fair values for awards of PSUs granted in the years ended December 31, 2019, 2018 and 2017, which included market-based metrics, were determined using a Monte Carlo simulation valuation methodology using the following key inputs:

	2019		2018		2017
Valuation date price based on March 8, 2019, February 28, 2018 and March 22, 2017 closing stock prices of Quanta common stock	$35.19		$34.44		$36.31
Expected volatility	25	%	34	%	36	%
Risk-free interest rate	2.43	%	2.39	%	1.46	%
Term in years	2.81		2.84		2.78