Stock-Based Compensation

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

We grant stock-based compensation awards, including stock options, restricted stock units, phantom stock, and unrestricted stock units, under the Second Amended and Restated 2010 Stock Incentive Plan (Stock Incentive Plan). In the Stock Incentive Plan, we have 12,623,538 shares of common stock reserved and authorized for issuance subject to stock splits, dividends, and other similar events, and, at June 30, 2021, 5,345,201 shares were available for grant. We issue new shares of common stock upon the exercise of stock options or when vesting conditions on restricted stock units are fully satisfied. These shares are subject to a fungible share provision such that the authorized share available for grant is reduced by (i) one share for every one share subject to a stock option or share appreciation right granted under the Plan and (ii) 1.7 shares for every one share of common stock that was subject to an award other than an option or share appreciation right.

We also periodically award phantom stock units, which are settled in cash upon vesting and accounted for as liability-based awards, with no impact to the shares available for grant.

In addition, we maintain the Employee Stock Purchase Plan (ESPP), for which 160,181 shares of common stock were available for future issuance at June 30, 2021.

ESPP activity and stock-based grants other than stock options and restricted stock units were not significant for the three and six months ended June 30, 2021 and 2020.

Stock-Based Compensation Expense

Total stock-based compensation expense and the related tax benefit were as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
In thousands	2021		2020		2021		2020
Stock options	$	371	$	526	$	711	$	993
Restricted stock units	5,511		6,367		11,442		14,176
Unrestricted stock awards	206		206		433		412
Phantom stock units	1,225		1,060		2,342		1,493
Total stock-based compensation	$	7,313	$	8,159	$	14,928	$	17,074

Related tax benefit	$	1,318	$	1,420	$	2,681	$	3,187

Stock Options

A summary of our stock option activity is as follows:


	Shares	Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value		Weighted Average Grant Date Fair Value
	(in thousands)			(years)	(in thousands)
Outstanding, January 1, 2020	458	$	56.38	7.0	$	12,641

Granted	73	87.27					$	26.72
Exercised	(47)	51.52			1,131


Outstanding, June 30, 2020	484	$	61.48	7.3	$	4,871

Outstanding, January 1, 2021	433	$	61.95	6.9	$	14,697
Granted	—						$	—
Exercised	(31)	66.97			1,121

Forfeited	(6)	83.33
Outstanding, June 30, 2021	396	$	61.25	6.4	$	15,349

Exercisable, June 30, 2021	288	$	54.75	5.6	$	13,048

At June 30, 2021, total unrecognized stock-based compensation expense related to nonvested stock options was $1.7 million, which is expected to be recognized over a weighted average period of approximately 1.5 years.

The weighted average assumptions used to estimate the fair value of stock options granted and the resulting weighted average fair value are as follows:


	Six Months Ended June 30,
		2021		2020

Expected volatility		—	%	31.0	%
Risk-free interest rate		—	%	1.4	%
Expected term (years)		N/A		5.3

There were no employee stock options granted for the three and six months ended June 30, 2021, and the three months ended June 30, 2020.

Restricted Stock Units

The following table summarizes restricted stock unit activity:


In thousands, except fair value	Number of Restricted Stock Units	Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value
Outstanding, January 1, 2020	684

Granted	189	$	85.97
Released (1)	(230)			$	2,506
Forfeited	(13)
Outstanding, June 30, 2020	630

Outstanding, January 1, 2021	544	$	71.79
Granted	203	98.94
Released (1)	(194)	73.35		$	19,474
Forfeited	(33)	73.65
Outstanding, June 30, 2021	520	81.98

Vested but not released, June 30, 2021	10			$	989

(1) Shares released is presented as gross shares and does not reflect shares withheld by us for employee payroll tax obligations.

At June 30, 2021, total unrecognized compensation expense on restricted stock units was $36.4 million, which is expected to be recognized over a weighted average period of approximately 1.9 years.

The weighted average assumptions used to estimate the fair value of performance-based restricted stock units granted with a service and market condition and the resulting weighted average fair value are as follows:


	Six Months Ended June 30,
		2021			2020

Expected volatility		50.5		%	37.6		%
Risk-free interest rate		0.2		%	1.5		%
Expected term (years)		2.9			1.8

Weighted average fair value		$	113.75		$	94.28

There were no performance-based restricted stock units granted for the three months ended June 30, 2021 and 2020.