Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock
Common stock, beginning balance (in shares) at Jul. 31, 2018		38,860,571
Beginning balance at Jul. 31, 2018	$ 505,684,000	$ 3,886,000	$ 538,453,000	$ 405,194,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jul. 31, 2018					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	3,356,000		3,356,000
Proceeds from exercises of stock options (in shares)		6,100
Proceeds from exercises of stock options	174,000	$ 1,000	173,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		32,035
Proceeds from issuance of employee stock purchase plan shares	709,000	$ 3,000	706,000
Issuance of restricted stock (in shares)		10,386
Issuance of restricted stock, net	$ 0	$ 1,000	(1,000)
Net settlement of stock-based awards (in shares)	9,345	53,438
Net settlement of stock-based awards	$ (2,069,000)	$ 5,000	(2,074,000)
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	(7,169,000)			(7,169,000)
Accrual of dividend equivalents, net of reversal	(248,000)			(248,000)
Net income	18,906,000			18,906,000
Common stock, ending balance (in shares) at Apr. 30, 2019		39,171,199
Ending balance at Apr. 30, 2019	524,949,000	$ 3,917,000	546,198,000	416,683,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Apr. 30, 2019					15,033,317
Common stock, beginning balance (in shares) at Jan. 31, 2019		38,950,547
Beginning balance at Jan. 31, 2019	512,877,000	$ 3,895,000	539,273,000	411,558,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jan. 31, 2019					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	1,119,000		1,119,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		11,837
Proceeds from issuance of employee stock purchase plan shares	233,000	$ 1,000	232,000
Net settlement of stock-based awards (in shares)		146
Net settlement of stock-based awards	(11,000)		(11,000)
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	(2,405,000)			(2,405,000)
Accrual of dividend equivalents, net of reversal	(82,000)			(82,000)
Net income	7,612,000			7,612,000
Common stock, ending balance (in shares) at Apr. 30, 2019		39,171,199
Ending balance at Apr. 30, 2019	$ 524,949,000	$ 3,917,000	546,198,000	416,683,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Apr. 30, 2019					15,033,317
Common stock, beginning balance (in shares) at Jul. 31, 2019	39,276,161	39,276,161
Beginning balance at Jul. 31, 2019	$ 535,082,000	$ 3,928,000	552,670,000	420,333,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jul. 31, 2019	15,033,317				15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	$ 3,098,000		3,098,000
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)		36,168
Proceeds from issuance of employee stock purchase plan shares	690,000	$ 4,000	686,000
Issuance of restricted stock (in shares)		3,319
Issuance of restricted stock, net	$ 0	$ 0	0
Net settlement of stock-based awards (in shares)	27,992	109,405
Net settlement of stock-based awards	$ (3,487,000)	$ 11,000	(3,498,000)
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	(7,326,000)			(7,326,000)
Accrual of dividend equivalents, net of reversal	(169,000)			(169,000)
Net income	$ 5,894,000			5,894,000
Common stock, ending balance (in shares) at Apr. 30, 2020	39,765,257	39,765,257
Ending balance at Apr. 30, 2020	$ 545,825,000	$ 3,977,000	564,965,000	418,732,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Apr. 30, 2020	15,033,317				15,033,317
Common stock, beginning balance (in shares) at Jan. 31, 2020		39,752,559
Beginning balance at Jan. 31, 2020	$ 551,203,000	$ 3,975,000	563,834,000	425,243,000	$ (441,849,000)
Treasury stock, beginning balance (in shares) at Jan. 31, 2020					15,033,317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	981,000		981,000
Proceeds from issuance of employee stock purchase plan shares (in shares)		16,158
Proceeds from issuance of employee stock purchase plan shares	180,000	$ 2,000	178,000
Forfeiture of restricted stock (in shares)		(5,539)
Forfeiture of restricted stock	0	$ (1,000)	1,000
Net settlement of stock-based awards (in shares)		2,079
Net settlement of stock-based awards	(28,000)	$ 1,000	(29,000)
Cash dividends declared	(2,466,000)			(2,466,000)
Accrual of dividend equivalents, net of reversal	(56,000)			(56,000)
Net income	$ (3,989,000)			(3,989,000)
Common stock, ending balance (in shares) at Apr. 30, 2020	39,765,257	39,765,257
Ending balance at Apr. 30, 2020	$ 545,825,000	$ 3,977,000	$ 564,965,000	$ 418,732,000	$ (441,849,000)
Treasury stock, ending balance (in shares) at Apr. 30, 2020	15,033,317				15,033,317