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Income Taxes - Additional Information (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2018 | Sep. 30, 2017
Income Taxes [Line Items] |  |  |  |  |
United States statutory tax rate | 35.00% | 21.00% | 21.00% |  |
Cash and cash equivalents held by foreign subsidiaries |  | $ 5,200 |  |  |
Temporary difference related to undistributed earnings |  | 6,500 | $ 11,600 |  |
Unrecognized tax liabilities |  | 0 | 0 |  |
Valuation allowance against net deferred tax assets |  | 2,893 | 4,882 |  |
United States |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss, carryforwards |  | 101,400 |  |  | $ 28,300
Net operating loss, carryforwards expiration year |  |  |  |  | 2028
Tax Cuts And Jobs Act Of 2017, change in tax rate income tax expense benefit |  |  |  | $ 73,100 |
Valuation allowance against net deferred tax assets |  | 31,600 | 25,700 |  |
Canada |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss, carryforwards |  | $ 20,200 |  |  |
Net operating loss, carryforwards expiration year |  | 2033 |  |  |
Valuation allowance against net deferred tax assets |  | $ 5,400 | 5,600 |  |
Russia |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss, carryforwards |  | $ 1,500 |  |  |
Net operating loss, carryforwards expiration year |  | 2026 |  |  |
Valuation allowance against net deferred tax assets |  | $ 300 | $ 200 |  |

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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.Fact.4) -URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)(2)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319 + Details
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