CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Current assets:
Allowance for doubtful accounts	$ 583	$ 2,377
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)	39,914,000	39,592,000
Treasury stock (in shares)	10,834,000	10,491,000