Schedule II - Valuation and Qualifying Accounts - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Allowance for Doubtful Accounts for Long-term Accounts Receivable | Other Assets
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for doubtful accounts for long-term accounts receivable	$ 981	$ 13,568