Stock-Based Compensation (Tables)

12 Months Ended

Jul. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of the components of stock-based compensation expense recognized in the consolidated statements of income

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

	Year Ended July 31,
	2020		2019		2018
Cost of sales	$	1,255	$	1,010	$	663
Operating expenses:
Selling	2,606		2,428		1,458
General and administrative	7,803		11,828		7,292
Research and development	412		296		202
Total operating expenses	10,821		14,552		8,952
Stock-based compensation expense	$	12,076	$	15,562	$	9,615

Schedule of weighted-average assumuptions 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:

	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 fiscal 2020, 2019 and 2018 follows:

	Number of Time-based Shares	Number of Performance-based Shares	Number of Market-based Shares	Number of Total Shares	Weighted Average Fair Value
Nonvested stock awards at August 1, 2017	196,818	16,235	9,245	222,298	$	66.28
Granted	94,309	17,486	10,465	122,260	$	101.74
Vested(1)	(115,943)	(5,845)	—	(121,788)	$	60.25
Forfeited	(6,864)	(1,800)	(2,000)	(10,664)	$	95.09
Nonvested stock awards at July 31, 2018	168,320	26,076	17,710	212,106	$	88.87
Granted	188,431	35,981	25,320	249,732	$	85.16
Vested(1)	(105,516)	(13,327)	(5,265)	(124,108)	$	80.44
Forfeited	(16,371)	(8,520)	(5,686)	(30,577)	$	96.54
Nonvested stock awards at July 31, 2019	234,864	40,210	32,079	307,153	$	88.99
Granted	233,701	—	47,967	281,668	$	68.71
Vested(1)	(121,852)	(8,954)	(3,462)	(134,268)	$	87.14
Forfeited	(28,011)	(2,082)	(12,745)	(42,838)	$	82.59
Nonvested stock awards at July 31, 2020	318,702	29,174	63,839	411,715	$	76.29

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(1)The aggregate fair value of all nonvested stock awards which vested was approximately $11,701, $9,985 and 7,338 in fiscal 2020, 2019 and 2018, respectively.

Summary of stock option activity

A summary of stock option activity for fiscal 2020, 2019 and 2018 follows:

	Number of shares	Weighted Average Exercise Price		Weighted Average Contractual Life Remaining	Aggregate Intrinsic Value
Outstanding at August 1, 2017	122,500	$	29.36
Exercised	(52,500)	$	17.04
Outstanding at July 31, 2018	70,000	$	38.60
Exercised	(30,000)	$	31.81
Outstanding at July 31, 2019	40,000	$	43.70
Exercised	(25,000)	$	36.70
Outstanding at July 31, 2020	15,000	$	55.36	0.2 years	$	—
Exercisable at July 31, 2020 (out of the money)	15,000	$	55.36	0.2 years	$	—