Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Beginning balance (in shares) at Jul. 31, 2019			39,276,161
Beginning balance (in shares) at Jul. 31, 2019							15,033,317
Beginning 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	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
Net settlement of stock-based awards (in shares)			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, net	(7,326,000)				(7,326,000)
Accrual of dividend equivalents, net of reversal	(169,000)				(169,000)
Net (loss) income	5,894,000				5,894,000
Ending balance (in shares) at Apr. 30, 2020			39,765,257
Ending balance (in shares) at Apr. 30, 2020							15,033,317
Ending balance at Apr. 30, 2020	545,825,000		$ 3,977,000	564,965,000	418,732,000		$ (441,849,000)
Beginning balance (in shares) at Jan. 31, 2020			39,752,559
Beginning balance (in shares) at Jan. 31, 2020							15,033,317
Beginning balance at Jan. 31, 2020	551,203,000		$ 3,975,000	563,834,000	425,243,000		$ (441,849,000)
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, net	(2,466,000)				(2,466,000)
Accrual of dividend equivalents, net of reversal	(56,000)				(56,000)
Net (loss) income	(3,989,000)				(3,989,000)
Ending balance (in shares) at Apr. 30, 2020			39,765,257
Ending balance (in shares) at Apr. 30, 2020							15,033,317
Ending balance at Apr. 30, 2020	$ 545,825,000		$ 3,977,000	564,965,000	418,732,000		$ (441,849,000)
Beginning balance (in shares) at Jul. 31, 2020	39,924,439		39,924,439
Beginning balance (in shares) at Jul. 31, 2020	15,033,317						15,033,317
Beginning balance at Jul. 31, 2020	$ 549,299,000	$ (215,000)	$ 3,992,000	569,891,000	417,265,000	$ (215,000)	$ (441,849,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	3,190,000			3,190,000
Proceeds from issuance of employee stock purchase plan shares (in shares)			43,235
Proceeds from issuance of employee stock purchase plan shares	574,000		$ 4,000	570,000
Issuance of restricted stock (in shares)			35,495
Issuance of restricted stock	0		$ 4,000	(4,000)
Net settlement of stock-based awards (in shares)			72,479
Net settlement of stock-based awards	(1,400,000)		$ 7,000	(1,407,000)
Common stock issued for acquisitions (in shares)			1,026,567
Common stock issued for acquisitions	28,892,000		$ 103,000	28,789,000
Cash dividends declared, net	(7,588,000)				(7,588,000)
Accrual of dividend equivalents, net of reversal	(287,000)				(287,000)
Net (loss) income	$ (80,843,000)				(80,843,000)
Ending balance (in shares) at Apr. 30, 2021	41,102,215		41,102,215
Ending balance (in shares) at Apr. 30, 2021	15,033,317						15,033,317
Ending balance at Apr. 30, 2021	$ 491,622,000		$ 4,110,000	601,029,000	328,332,000		$ (441,849,000)
Beginning balance (in shares) at Jan. 31, 2021			40,059,977
Beginning balance (in shares) at Jan. 31, 2021							15,033,317
Beginning balance at Jan. 31, 2021	463,284,000		$ 4,006,000	570,891,000	330,236,000		$ (441,849,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity-classified stock award compensation	1,204,000			1,204,000
Proceeds from issuance of employee stock purchase plan shares (in shares)			12,113
Proceeds from issuance of employee stock purchase plan shares	205,000		$ 1,000	204,000
Forfeiture of restricted stock (in shares)			(480)
Net settlement of stock-based awards (in shares)			4,038
Net settlement of stock-based awards	(59,000)			(59,000)
Common stock issued for acquisitions (in shares)			1,026,567
Common stock issued for acquisitions	28,892,000		$ 103,000	28,789,000
Cash dividends declared, net	(2,600,000)				(2,600,000)
Accrual of dividend equivalents, net of reversal	(96,000)				(96,000)
Net (loss) income	$ 792,000				792,000
Ending balance (in shares) at Apr. 30, 2021	41,102,215		41,102,215
Ending balance (in shares) at Apr. 30, 2021	15,033,317						15,033,317
Ending balance at Apr. 30, 2021	$ 491,622,000		$ 4,110,000	$ 601,029,000	$ 328,332,000		$ (441,849,000)