STOCK-BASED COMPENSATION

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Total stock-based compensation cost charged to selling, general and administrative expenses for the three and six months ended June 30, 2021 was $3.3 million and $6.8 million, respectively. Total stock-based compensation cost charged to selling, general and administrative expenses for the three and six months ended June 30, 2020 was $2.8 million and $6.1 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense for the three and six months ended June 30, 2021 was $0.8 million and $1.5 million, respectively. The total income tax benefit recognized in the consolidated statements of operations from stock-based compensation expense for the three and six months ended June 30, 2020 was $0.4 million and $1.2 million, respectively.

Restricted Stock Awards

The following table summarizes information about restricted stock awards for the six months ended June 30, 2021:


Restricted Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2021	493,879	$	59.74
Granted	51,354	87.86
Vested	(103,449)	57.35
Forfeited	(32,321)	58.87
Balance at June 30, 2021	409,463	63.94

As of June 30, 2021, there was $17.8 million of total unrecognized compensation cost arising from restricted stock awards. This cost is expected to be recognized over a weighted average period of 2.5 years. The total fair value of restricted stock vested during the three and six months ended June 30, 2021 was $4.9 million and $8.9 million, respectively. The total fair value of restricted stock vested during the three and six months ended June 30, 2020 was $4.4 million and $9.7 million, respectively.

Performance Stock Awards

Performance stock awards are subject to performance criteria established by the Compensation Committee of the Company's Board of Directors prior to or at the date of grant. The vesting of the performance stock awards is based on achieving targets currently based on revenue, Adjusted EBITDA, Adjusted EBITDA Margin, Adjusted Free Cash Flow and Total Recordable Incident Rate. In addition, performance stock awards include continued service conditions.

The following table summarizes information about performance stock awards for the six months ended June 30, 2021:


Performance Stock	Number of Shares	Weighted Average Grant-Date Fair Value
Balance at January 1, 2021	254,449	$	61.75
Granted	5,897	86.15
Vested	(71,815)	62.27
Forfeited	(20,003)	61.54
Balance at June 30, 2021	168,528	62.41

As of June 30, 2021, there was $1.8 million of total unrecognized compensation cost arising from unvested performance stock awards deemed probable of vesting. No performance awards vested during the three months ended June 30, 2021 and June 30, 2020. The total fair value of performance awards vested during the six months ended June 30, 2021 and June 30, 2020 was $6.4 million and $1.3 million, respectively.