Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Taxes [Line Items]
United States statutory tax rate	35.00%	21.00%	24.00%
Tax refund resulting from filing of an amended U.S. tax return			$ 700
Decrease in deferred tax asset due to Tax Act			8,100
Cash and cash equivalents held by foreign subsidiaries		$ 7,000
Temporary difference related to undistributed earnings		12,900	12,900
unrecognized tax liabilities		0	0
Valuation allowance against net deferred tax assets		964	(4,237)
United States
Income Taxes [Line Items]
Net operating loss, carryforwards		61,700		$ 41,400
Net operating loss, carryforwards expiration year				2028
Tax Cuts And Jobs Act Of 2017, change in tax rate income tax expense benefit			17,500
Valuation allowance against net deferred tax assets		21,500	20,900
Canada
Income Taxes [Line Items]
Net operating loss, carryforwards		$ 15,200
Net operating loss, carryforwards expiration year		2033
Valuation allowance against net deferred tax assets		$ 4,500	$ 4,400
Russia
Income Taxes [Line Items]
Net operating loss, carryforwards		$ 500
Net operating loss, carryforwards expiration year		2026