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Income Taxes - Changes to Deferred Tax Asset Valuation Allowance (Details) - USD ($) $ in Millions | 12 Months Ended
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Oct. 31, 2019 | Oct. 31, 2018 | Oct. 31, 2017
Operating Loss Carryforwards, Valuation Allowance Rollforward [Roll Forward] |  |  |
Valuation allowance at beginning of year | $ 12.0 | $ 7.7 | $ 5.4
GCA acquisition | 0.0 | 2.4 | 4.1
Other, net | (3.6) | 1.8 | (1.8)
Valuation allowance at end of year | $ 8.4 | $ 12.0 | $ 7.7

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