Income Taxes - Narrative (Details) - USD ($) |
3 Months Ended | 6 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Apr. 30, 2018 |
Jan. 31, 2018 |
Apr. 30, 2017 |
Apr. 30, 2018 |
Apr. 30, 2017 |
Oct. 31, 2018 |
|
| Income Taxes [Line Items] | ||||||
| Net discrete tax benefit from remeasurement of deferred taxes at new rate due to Tax Act | $ 28,700,000 | |||||
| One-time transition tax on deemed repatriation of indefinitely reinvested earnings | $ 7,000,000 | |||||
| Tax deductions for energy efficient government buildings | $ 2,000,000 | $ 2,300,000 | ||||
| Increase (decrease) in tax credits, work opportunity tax credit | $ 1,500,000 | 1,500,000 | ||||
| Discrete tax benefit related to enactment of Tax Act | 21,700,000 | |||||
| Income tax benefit related to vesting of share-based compensation awards | $ 2,100,000 | $ 1,500,000 | $ 2,100,000 | |||
| Forecast | ||||||
| Income Taxes [Line Items] | ||||||
| U.S. statutory federal rate (percent) | 23.30% | |||||