Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Beginning balance (in shares) at Jul. 31, 2017		38,619,467
Beginning balance (in shares) at Jul. 31, 2017					15,033,317
Beginning balance at Jul. 31, 2017	$ 480,150,000	$ 3,862,000	$ 533,001,000	$ 385,136,000	$ (441,849,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	8,605,000		8,605,000
Proceeds from exercises of stock options (in shares)		13,100
Proceeds from exercises of stock options	326,000	$ 1,000	325,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		44,996
Proceeds from issuance of employee stock purchase plan shares	855,000	$ 5,000	850,000
Forfeiture of restricted stock (in shares)		(10,254)
Forfeiture of restricted stock	$ 0	$ (1,000)	1,000
Net settlement of stock-based awards (in shares)	8,706	193,262
Net settlement of stock-based awards	$ (4,310,000)	$ 19,000	(4,329,000)
Cash dividends declared	(9,411,000)			(9,411,000)
Accrual of dividend equivalents, net of reversal	(300,000)			(300,000)
Net income	29,769,000			29,769,000
Ending balance (in shares) at Jul. 31, 2018		38,860,571
Ending balance (in shares) at Jul. 31, 2018					15,033,317
Ending balance at Jul. 31, 2018	505,684,000	$ 3,886,000	538,453,000	405,194,000	$ (441,849,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	11,427,000		11,427,000
Proceeds from exercises of stock options (in shares)		8,100
Proceeds from exercises of stock options	216,000	$ 1,000	215,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		43,316
Proceeds from issuance of employee stock purchase plan shares	926,000	$ 4,000	922,000
Issuance of restricted stock, net (in shares)		10,386
Issuance of restricted stock	$ 0	$ 1,000	(1,000)
Net settlement of stock-based awards (in shares)	9,345	145,119
Net settlement of stock-based awards	$ (3,916,000)	$ 15,000	(3,931,000)
Common stock issued for acquisitions (in shares)		208,669
Common stock issued for acquisitions	5,606,000	$ 21,000	5,585,000
Cash dividends declared	(9,575,000)			(9,575,000)
Accrual of dividend equivalents, net of reversal	(327,000)			(327,000)
Net income	$ 25,041,000			25,041,000
Ending balance (in shares) at Jul. 31, 2019	39,276,161	39,276,161
Ending balance (in shares) at Jul. 31, 2019	15,033,317				15,033,317
Ending balance at Jul. 31, 2019	$ 535,082,000	$ 3,928,000	552,670,000	420,333,000	$ (441,849,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	9,275,000		9,275,000
Proceeds from exercises of stock options (in shares)		16,700
Proceeds from exercises of stock options	468,000	$ 2,000	466,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		52,958
Proceeds from issuance of employee stock purchase plan shares	855,000	$ 5,000	850,000
Issuance of restricted stock, net (in shares)		3,319
Issuance of restricted stock	$ 0	$ 0	0
Net settlement of stock-based awards (in shares)	27,994	251,797
Net settlement of stock-based awards	$ (4,888,000)	$ 25,000	(4,913,000)
Common stock issued for acquisitions (in shares)		323,504
Common stock issued for acquisitions	11,575,000	$ 32,000	11,543,000
Cash dividends declared	(9,794,000)			(9,794,000)
Accrual of dividend equivalents, net of reversal	(294,000)			(294,000)
Net income	$ 7,020,000			7,020,000
Ending balance (in shares) at Jul. 31, 2020	39,924,439	39,924,439
Ending balance (in shares) at Jul. 31, 2020	15,033,317				15,033,317
Ending balance at Jul. 31, 2020	$ 549,299,000	$ 3,992,000	$ 569,891,000	$ 417,265,000	$ (441,849,000)