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Fair Value (Details) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Apr. 30, 2019 | Oct. 31, 2020
Fair Value Disclosures [Abstract] |  |
Fair Value, Assets, Measured On Nonrecurring Basis Change In Unrealized Gain (Loss) | $ 0 | $ 0

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