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Fair Value of Financial Instruments - Discount Rate (Details) - Discount Rates | Apr. 30, 2020
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Valuation, Income Approach | Education |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
Reporting unit, measurement input | 0.100
Valuation, Income Approach | Aviation |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
Reporting unit, measurement input | 0.105
Valuation, Income Approach | Technical Solutions |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
Reporting unit, measurement input | 0.110
Valuation, Market Approach |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |
Reporting unit, measurement input | 0.150

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