CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Current assets:
Allowance for doubtful accounts	$ 1,900	$ 1,747
LIABILITIES AND STOCKHOLDERS' EQUITY
Long-term debt, prepaid debt issuance cost	$ 0	$ 441
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)	35,862,465	35,230,742
Treasury stock at cost (in shares)	10,356,147	9,948,190