Stock-Based Compensation (Tables)

3 Months Ended

Oct. 31, 2017

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

Schedule of the income statement components of stock-based compensation expense recognized in the Condensed Consolidated Statements of Income

The following table shows the income statement components of stock-based compensation expense recognized in the condensed consolidated statements of income:

	Three Months Ended October 31,
	2017		2016
Cost of sales	$	115	$	110
Operating expenses:
Selling	365		629
General and administrative	1,333		2,153
Research and development	38		30
Total operating expenses	1,736		2,812
Stock-based compensation before income taxes	$	1,851	$	2,922

Schedule of weighted-average assumptions used to estimate fair value of stock options

We determine the fair value of each stock award with market conditions using a Monte Carlo simulation on the date of grant using the following assumptions:

	Three Months Ended October 31,
	2017		2016
Volatility of common stock	26.60	%	27.75	%
Average volatility of peer companies	33.72	%	32.98	%
Average correlation coefficient of peer companies	32.26	%	35.35	%
Risk-free interest rate	1.62	%	0.96	%

Summary of nonvested stock award activity

A summary of nonvested stock award activity for the three months ended October 31, 2017 follows:

	Number of Time-based Shares		Number of Performance-based Shares		Number of Market-based Shares	Number of Total Shares		Weighted Average Fair Value
July 31, 2017	196,818		16,235		9,245	222,298		$	66.28
Granted	91,234		18,647		10,465	120,346		$	101.55
Vested(1)	(80,931	)	(4,834	)	—	(85,765	)	$	57.72
Forfeited	(1,315	)	—		—	(1,315	)	$	76.81
October 31, 2017	205,806		30,048		19,710	255,564		$	85.76

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(1) The aggregate fair value of all nonvested stock awards which vested was approximately $4,950.

Summary of stock option activity

A summary of stock option activity for the three months ended October 31, 2017 follows:

	Number of shares		Weighted Average Exercise Price		Weighted Average Contractual Life Remaining (Years)	Aggregate Intrinsic Value
Outstanding at July 31, 2017	122,500		$	29.36
Granted	—		—
Exercised	(52,500	)	17.04
Outstanding at October 31, 2017	70,000		$	38.60	1.79	$	4,221
Exercisable at October 31, 2017	65,000		$	37.31	1.69	$	4,003