Stock-Based Compensation (Tables)

9 Months Ended

Apr. 30, 2020

Share-based Payment Arrangement [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 components of stock-based compensation expense recognized in the condensed consolidated statements of income:

	Three Months Ended April 30,				Nine Months Ended April 30,
	2020		2019		2020		2019
Cost of sales	$	328	$	245	$	978	$	769
Operating expenses:
Selling	657		538		1,802		1,684
General and administrative	1,931		4,874		5,764		9,249
Research and development	111		65		299		183
Total operating expenses	2,699		5,477		7,865		11,116
Stock-based compensation expense	$	3,027	$	5,722	$	8,843	$	11,885

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

We determined the fair value of our market-based restricted stock awards using a Monte Carlo simulation on the date of grant using the following assumptions:

	Nine Months Ended April 30,
	2020		2019
Volatility of common stock	30.73	%	27.54	%
Average volatility of peer companies	36.28	%	36.55	%
Average correlation coefficient of peer companies	24.63	%	27.18	%
Risk-free interest rate	1.49	%	2.93	%

Summary of nonvested stock award activity

A summary of nonvested stock award activity for the nine months ended April 30, 2020 follows:

	Number of Time-based Awards	Number of Performance-based Awards	Number of Market-based Awards	Number of Total Awards	Weighted Average Fair Value
Nonvested stock awards at July 31, 2019	234,864	40,210	32,079	307,153	$	88.99
Granted	212,391	—	47,967	260,358	$	73.50
Vested(1)	(100,184)	(8,909)	(3,462)	(112,555)	$	89.28
Forfeited	(25,716)	(1,850)	(12,555)	(40,121)	$	82.89
Nonvested stock awards at April 30, 2020	321,355	29,451	64,029	414,835	$	79.69

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(1)The aggregate fair value of all nonvested stock awards which vested was approximately $10,049.

Summary of stock option activity

A summary of stock option activity for the nine months ended April 30, 2020 follows:

	Number of shares	Weighted Average Exercise Price		Weighted Average Contractual Life Remaining (Years)	Aggregate Intrinsic Value
Outstanding at July 31, 2019	40,000	$	43.70
Exercised	(25,000)	$	36.70
Outstanding at April 30, 2020	15,000	$	55.36	0.45	$	—
Exercisable at 4/30/2020 (out of the money)	15,000	$	55.36	0.45	$	—