Income taxes - Reconciliation of Tax Provision Using the Federal Statutory Income Tax Rate to Reported Provision (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
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Sep. 30, 2019 |
Sep. 30, 2018 |
Sep. 30, 2017 |
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| Reconciliation of actual provision for income taxes and provision for income taxes resulting from the use of federal statutory income tax | |||
| Federal income tax provision at statutory rate of 21%, 24.5% and 35%, respectively | $ 66,637 | $ 73,396 | $ 109,982 |
| State income taxes, net of federal benefit | 14,825 | 12,348 | 10,554 |
| Foreign taxation | 1,210 | (1,531) | (6,940) |
| Permanent items | 2,682 | 1,176 | 970 |
| Tax credits | (3,730) | (2,438) | (4,851) |
| Toll tax | (481) | 9,425 | 0 |
| Deferred tax liability - tax rate change | 0 | (10,514) | 0 |
| Vesting of equity compensation | (4,783) | (2,849) | (6,569) |
| Other | 465 | (620) | (1,093) |
| Provision for income taxes | $ 76,825 | $ 78,393 | $ 102,053 |
| Statutory income tax rate (as a percent) | 21.00% | 24.50% | 35.00% |
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- Definition Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Transition Tax on Accumulated Foreign Earnings, Amount No definition available.
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- References No definition available.
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to foreign income tax expense (benefit). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to nondeductible expenses. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to nondeductible equity-based compensation costs. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to state and local income tax expense (benefit). Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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