UNAUDITED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Current assets
Allowance for doubtful accounts	$ 1,785	$ 1,747
LIABILITIES AND STOCKHOLDERS' EQUITY
Long-term debt, prepaid debt issuance cost	$ 378	$ 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)	35,471,403	35,230,742
Treasury stock at cost, shares (in shares)	9,999,034	9,948,190