Reconciliation of Income Taxes at United States Rate to Effective Tax Rate (Detail)	12 Months Ended
Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Income Tax Disclosure [Abstract]
U.S. Federal statutory tax rate (%)	35.00%	35.00%	35.00%
State income taxes, net of federal tax benefit	1.00%	(2.00%)	(1.00%)
Domestic production benefit			1.00%
General business credit (U.S. R&D)	2.00%	(5.00%)	(2.00%)
Valuation allowance	(25.00%)	2.00%
Asset impairment	(27.00%)
Effect of international operations	3.00%	(3.00%)	(11.00%)
Increase (decrease) in tax reserves	2.00%	8.00%	(6.00%)
Non-deductible royalty		2.00%
Other items, net	(3.00%)	3.00%	2.00%
Effective tax rate (%)	(12.00%)	40.00%	18.00%

Effective Income Tax Rate Reconciliation, Increase (Decrease), in Tax Reserves

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Effective Income Tax Rate Reconciliation Non Deductible Royalty

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Effective Income Tax Rate Reconciliation Nondeductible Expense Benefit Research and Development

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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