Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement, Noncash Expense [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 December 31, 2020, 5,597,418 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 ESPP, for which 178,159 shares of common stock were available for future issuance at December 31, 2020.

ESPP activity and stock-based grants other than stock options and restricted stock units were not significant for the years ended December 31, 2020, 2019, and 2018.

Stock-Based Compensation Expense

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


	Year Ended December 31,
In thousands	2020		2019		2018
Stock options	$	1,944	$	1,770	$	3,675
Restricted stock units	22,285		24,560		26,859
Unrestricted stock awards	824		630		729
Phantom stock units	3,720		3,301		2,165
Total stock-based compensation	$	28,773	$	30,261	$	33,428

Related tax benefit	$	5,086	$	5,390	$	6,019

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, 2018	956	$	47.10	6.3	$	21,965

Converted upon acquisition	42	51.86					$	14.86
Granted	122	68.21					24.29
Exercised	(152)	38.99			4,520
Forfeited	(7)	60.03
Expired	(66)	95.31
Outstanding, December 31, 2018	895	$	47.93	6.2	$	4,806


Granted	76	76.55					$	26.20
Exercised	(489)	43.55			15,759
Forfeited	(13)	67.34
Expired	(11)	66.24
Outstanding, December 31, 2019	458	$	56.38	7.0	$	12,641


Granted	83	84.39					$	26.37
Exercised	(103)	53.99			2,061
Forfeited	(5)	83.94
Outstanding, December 31, 2020	433	$	61.95	6.9	$	14,697

Exercisable, December 31, 2020	268	$	51.85	5.8	$	11,810

At December 31, 2020, total unrecognized stock-based compensation expense related to nonvested stock options was $2.6 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 stock options granted and the resulting weighted average fair value are as follows:


	Year Ended December 31,
	2020		2019		2018
Expected volatility	32.3	%	31.7	%	30.5	%
Risk-free interest rate	1.3	%	1.7	%	2.8	%
Expected term (years)	5.3		6.1		6.1

Restricted Stock Units

The following table summarizes restricted stock unit activity:


	Number of Restricted Stock Units	Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value
	In thousands			In thousands
Outstanding, January 1, 2018	556	$	47.68

Converted upon acquisition	579	69.40
Granted	387	57.48
Released (1)	(593)			$	32,567
Forfeited	(112)
Outstanding, December 31, 2018	817	$	59.70


Granted	404	62.97
Released (1)	(471)			$	29,304
Forfeited	(66)
Outstanding, December 31, 2019	684	$	64.38

Granted	262	83.42
Released (1)	(363)	65.25		$	23,702
Forfeited	(39)	71.96
Outstanding, December 31, 2020	544	$	71.79

Vested but not released, December 31, 2020	50			$	4,836

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

At December 31, 2020, total unrecognized compensation expense on restricted stock units was $25.9 million, which is expected to be recognized over a weighted average period of approximately 1.7 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:


	Year Ended December 31,
	2020			2019			2018
Expected volatility	44.9		%	31.4		%	28.0		%
Risk-free interest rate	1.0		%	2.5		%	2.2		%
Expected term (years)	1.8			1.6			2.1

Weighted average fair value	$	93.97		$	61.25		$	78.56

Phantom Stock Units

The following table summarizes phantom stock unit activity:


	Number of Phantom Stock Units	Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value
	In thousands			In thousands
Outstanding, January 1, 2018	63	$	62.53
Converted upon acquisition	21
Granted	41	66.67
Released	(35)			$	2,409
Forfeited	(7)
Outstanding, December 31, 2018	83	$	61.80




Converted upon acquisition	—
Granted	55	60.49
Released	(42)			$	2,625
Forfeited	(7)
Outstanding, December 31, 2019	89	$	62.85




Granted	38	87.27
Released	(40)	63.87		$	2,971
Forfeited	(5)	70.99
Outstanding, December 31, 2020	82	$	73.13

At December 31, 2020, total unrecognized compensation expense on phantom stock units was $5.2 million, which is expected to be recognized over a weighted average period of approximately 1.8 years. As of December 31, 2020 and 2019, we have recognized a phantom stock liability of $2.7 million and $2.3 million within wages and benefits payable in the Consolidated Balance Sheets.