CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Statement of Financial Position [Abstract]
Allowances for returns and doubtful accounts	$ 1,137,332	$ 1,050,361
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, authorized (shares)	600,000,000	600,000,000
Common stock, issued (shares)	281,436,890	280,584,076
Common stock, outstanding (shares)	218,500,798	217,993,598
Treasury stock (shares)	62,936,092	62,590,478