Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 three months ended March 31, 2018:

	Stock Awards Granted		Weighted-Average Grant Price Per Share
Time-based restricted stock units		12,708	$	112.42
Performance-based restricted stock units (a)		39,511	$	70.42
Stock appreciation rights		10,630	$	112.42

(a) Includes 14,851 of target performance-based restricted stock unit awards granted during the three months ended March 31, 2018, and adjustments of 5,396, 13,583 and 5,681 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 three months ended March 31, 2018 and 2017 the data and assumptions shown in the following table were used:

	Three Months Ended March 31, 2018			Three Months Ended March 31, 2017
Weighted-average fair value of grants	$	44.17		$	27.81
Dividend yield		0	%		0	%
Average risk-free interest rate		2.7	%		2.0	%
Expected term (years)		5			5
Expected volatility		40.4	%		42.0	%

Summary of Stock-Based Compensation Expense

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

	Three Months Ended March 31,
	2018		2017
Stock appreciation rights	$	202	$	167
Time-based restricted stock and restricted stock units		822		737
Performance-based restricted stock and restricted stock units		1,249		1,039
Employee stock purchase plan		33		22
Total stock-based compensation	$	2,306	$	1,965