Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Current assets:
Allowance for doubtful accounts	$ 4,052	$ 3,946
Common stockholder’s equity:
Common stock, par value (in usd per share)	$ 2.25	$ 2.25
Common stock, shares authorized (in shares)	40,000,000	40,000,000
Common stock, shares issued (in shares)	26,781,785	26,781,785
Common stock, shares outstanding (in shares)	26,781,785	26,781,785