CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Current assets:
Allowance for doubtful accounts	$ 527	$ 583
Stockholders’ equity:
Common stock, authorized (in shares)	200,000,000	200,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, issued (in shares)	40,221,000	39,914,000
Treasury stock (in shares)	11,795,000	10,834,000