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Income Taxes (Details 4) - USD ($) $ in Thousands | 12 Months Ended
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Jul. 31, 2018 | Jul. 31, 2017 | Jul. 31, 2016
Reserves deducted from deferred income taxes, net: |  |  |
Valuation allowance - Balance at beginning of year | $ 129,872 | $ 130,498 | $ 127,449
Valuation allowance - Additions charged to costs and expenses |  | 16,017 | 3,049
Valuation allowance - Deductions | (53,852) | (16,643) |
Valuation allowance - Balance at end of year | $ 76,020 | $ 129,872 | $ 130,498

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