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