Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Sep. 30, 2018
Statement of Financial Position [Abstract]
Allowance for accounts receivable	$ 4,837	$ 6,217
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	160,000,000	160,000,000
Common stock, shares issued (in shares)	112,080,262	112,008,961
Common stock, shares outstanding (in shares)	109,433,198	108,993,718
Preferred stock, no par value (in dollars per share)	$ 0	$ 0
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, shares (in shares)	2,647,064	3,015,243