Summary of Significant Accounting Policies - Allowance of Uncollectible Amounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Allowance for Uncollectible Accounts [Roll Forward]
Balance at Beginning of Year	$ 40,228	$ 31,639	$ 22,810
Additions Charged to Costs and Expenses	14,482	13,209	14,940
Add: Discounts on Purchased Receivables	1,380	1,314	1,168
Deduct: Net Accounts Receivable Written-Off	19,795	5,934	7,279
Balance at End of Year	$ 36,295	$ 40,228	$ 31,639