Schedule II - Valuation and Qualifying Accounts (Details) - Allowances for returns and doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 1,223,887	$ 1,049,901	$ 1,068,251
Charged to Costs and Expenses	4,019,830	3,720,642	3,397,562
Deductions	(3,826,409)	(3,546,656)	(3,415,912)
Balance at End of Period	$ 1,417,308	$ 1,223,887	$ 1,049,901