Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock-Based Compensation Grants

The following table summarizes the Company’s stock-based compensation grants for the six months ended June 30, 2018:

	Stock Awards Granted		Weighted-Average Grant Price Per Share
Time-based restricted stock units		79,712	$	53.69
Performance-based restricted stock units (a)		79,022	$	35.21
Stock appreciation rights		21,260	$	56.21

(a) Includes 29,702 of target performance-based restricted stock unit awards granted during the six months ended June 30, 2018, and adjustments of 10,792, 27,166 and 11,362 grants due to the actual performance level achieved for restricted stock and restricted stock units awarded in 2015, 2016, and 2017, respectively.

Summary of Assumptions Used to Estimate Fair Value of Each SAR

The fair value of each SAR is estimated on the date of grant using a Black-Scholes option-pricing formula. For SARs issued in the six months ended June 30, 2018 and 2017 the data and assumptions shown in the following table were used:

	Six Months Ended June 30, 2018			Six Months Ended June 30, 2017
Weighted-average fair value of grants	$	22.09		$	13.91
Dividend yield		0	%		0	%
Average risk-free interest rate		2.7	%		2.01	%
Expected term (years)		5			5
Expected volatility		40.4	%		42.4	%

Summary of Stock-Based Compensation Expense

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Stock appreciation rights	$	56	$	25	$	259	$	192
Time-based restricted stock and restricted stock units		578		403		1,400		1,139
Performance-based restricted stock and restricted stock units		666		468		1,919		1,507
Employee stock purchase plan		45		16		67		38
Total stock-based compensation	$	1,345	$	912	$	3,645	$	2,876