Annual report pursuant to Section 13 and 15(d)

Revenue recognition - Accounts Receivable Reserves (Details)

v3.20.2
Revenue recognition - Accounts Receivable Reserves (Details) - Accounts receivable, billed and unbilled - USD ($)
$ in Thousands
12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2018
Changes in the reserves against current billed accounts receivable      
Balance at beginning of year $ 5,382 $ 4,285 $ 6,843
Additions to reserve 12,976 4,018 243
Deductions (12,307) (2,921) (2,801)
Balance at end of year $ 6,051 $ 5,382 $ 4,285