Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

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


	Year Ended December 31,
	2018		2017		2016
Time-based restricted stock and time-based restricted stock units	$	2,687	$	1,992	$	2,281
Performance-based restricted stock and performance-based restricted stock units		3,144		2,805		2,210
Stock appreciation rights		370		251		184
Employee stock purchase plan		143		139		113

Total stock-based compensation	$	6,344	$	5,187	$	4,788

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


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

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, 2018
Outstanding at December 31, 2015		524,154		$	6.57
Granted		—		$	—
Exercised		(248,704	)	$	5.55
Canceled		—		$	—

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		5.3	$	9,562,603
Vested at December 31, 2018		192,232		$	13.08		4.5	$	8,896,335
Exercisable at December 31, 2018		192,232		$	13.08		4.5	$	8,896,335

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, 2015		215,814		$	14.72
Granted		115,748		$	18.82
Vested		(87,696	)	$	21.17
Forfeited		(266	)	$	21.95

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

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, 2015		58,194		$	19.69
Granted		89,850		$	17.92
Vested		(29,898	)	$	17.86
Forfeited		(1,314	)	$	16.85

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