Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Stock-Based Compensation Expense

The following table summarizes the Company’s stock-based compensation expense (in thousands):

	Year Ended December 31,
	2019		2018		2017
Time-based restricted stock and restricted stock units	$	3,676	$	2,687	$	1,992
Performance-based restricted stock and restricted stock units		2,399		3,144		2,805
Stock appreciation rights		662		370		251
Employee stock purchase plan		193		143		139
Total stock-based compensation	$	6,930	$	6,344	$	5,187

Summary of Assumptions Used to Estimate Fair Value of Each SAR

For SARs issued in the years ended December 31, 2019, December 31, 2018 and December 31, 2017, respectively, the assumptions shown in the following table were used:

	Year Ended December 31,
	2019			2018			2017
Dividend yield		0	%		0	%		0	%
Average risk-free interest rate		2.5	%		2.7	%		2.0	%
Expected term (years)		5			5			5
Expected volatility		39.1	%		40.5	%		42.3	%

SAR Activity

SAR activity under the Plan and all predecessor stock incentive plans is as follows:

	SARs			Weighted-Average Grant Price Per Share		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value as of December 31, 2019
Outstanding at December 31, 2016		275,450		$	9.79
Granted		37,478		$	35.38
Exercised		(34,812	)	$	8.07
Canceled		—		$	—
Outstanding at December 31, 2017		278,116		$	13.45
Granted		21,260		$	56.59
Exercised		(60,900	)	$	5.27
Canceled		—		$	—
Outstanding at December 31, 2018		238,476		$	19.26
Granted		24,536		$	77.70
Exercised		(108,764	)	$	13.89
Canceled		(2,229	)	$	77.70
Outstanding at December 31, 2019		152,019		$	31.58		5.5	$	8,862,501
Vested at December 31, 2019		103,094		$	18.14		4.1	$	7,396,470
Exercisable at December 31, 2019		103,094		$	18.14		4.1	$	7,396,470

Time-Based Restricted Stock and Time-Based Restricted Stock Units [Member]

Restricted Stock Activity

Time-based restricted stock and restricted stock unit activity under the Plan and all predecessor stock incentive plans is as follows:

	Time-based Restricted Stock and Restricted Stock Unit			Weighted-Average Grant Price Per Share
Nonvested at December 31, 2016		243,600		$	15.80
Granted		72,402		$	36.27
Vested		(162,372	)	$	14.45
Forfeited		(512	)	$	18.68
Nonvested at December 31, 2017		153,118		$	26.90
Granted		87,264		$	54.72
Vested		(84,550	)	$	26.65
Forfeited		(284	)	$	35.05
Nonvested at December 31, 2018		155,548		$	42.68
Granted		35,650		$	76.23
Vested		(81,325	)	$	37.34
Forfeited		(640	)	$	62.33
Nonvested at December 31, 2019		109,233		$	57.49

Performance-Based Restricted Stock and Performance-Based Restricted Stock Units [Member]

Restricted Stock Activity

Performance-based restricted stock activity under the Plan is as follows:

	Performance-based Restricted Stock and Performance-based Restricted Stock Units			Weighted-Average Grant Price Per Share
Nonvested at December 31, 2016		116,832		$	18.32
Granted		86,614		$	28.77
Vested		(86,788	)	$	18.64
Forfeited		—		$	—
Nonvested at December 31, 2017		116,658		$	25.85
Granted		80,570		$	35.26
Vested		(106,022	)	$	23.52
Forfeited		—		$	—
Nonvested at December 31, 2018		91,206		$	36.86
Granted		82,135		$	47.64
Vested		(111,002	)	$	31.10
Forfeited		(511	)	$	58.45
Nonvested at December 31, 2019		61,828		$	61.34