Goodwill and Intangible Assets - Other Intangibles Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018	Jul. 31, 2018
Other Intangible Assets [Line Items]
Gross Carrying Amount	$ 71,852		$ 71,852		$ 81,460
Accumulated Amortization	(32,200)		(32,200)		(38,872)
Net Book Value	39,652		39,652		$ 42,588
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of Intangible Assets	1,434	$ 1,617	2,870	$ 3,310
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	5,717		5,717
Finite-Lived Intangible Assets, Amortization Expense, Year Two	5,191		5,191
Finite-Lived Intangible Assets, Amortization Expense, Year Three	5,151		5,151
Finite-Lived Intangible Assets, Amortization Expense, Year Four	5,006		5,006
Finite-Lived Intangible Assets, Amortization Expense, Year Five	2,025		$ 2,025
Patents
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			5 years		5 years
Gross Carrying Amount	1,448		$ 1,448		$ 1,448
Accumulated Amortization	(1,195)		(1,195)		(942)
Net Book Value	253		$ 253		$ 506
Trademarks and other
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			10 years		9 years
Gross Carrying Amount	2,467		$ 2,467		$ 4,497
Accumulated Amortization	(2,398)		(2,398)		(4,395)
Net Book Value	69		$ 69		$ 102
Customer relationships
Other Intangible Assets [Line Items]
Weighted Average Amortization Period			8 years		9 years
Gross Carrying Amount	48,465		$ 48,465		$ 55,999
Accumulated Amortization	(28,607)		(28,607)		(33,535)
Net Book Value	19,858		19,858		22,464
Trademarks
Other Intangible Assets [Line Items]
Gross Carrying Amount	19,472		19,472		19,516
Accumulated Amortization	0		0		0
Net Book Value	$ 19,472		$ 19,472		$ 19,516