Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 7,921	$ 5,599	$ 12,534
Accumulated depreciation and amortization	$ 961,006	$ 929,130	$ 918,311
Common stock, par value (in usd per share)	$ 2.25	$ 2.25	$ 2.25
Common stock, shares authorized (in shares)	40,000,000	40,000,000	40,000,000
Common stock, shares issued (in shares)	26,781,785	26,781,785	26,781,785
Common stock, shares outstanding (in shares)	26,781,785	26,781,785	26,781,785