Supplemental Cash Flow Information - Supplemental Disclosure of Non-cash Activity (Details) - USD ($) $ in Thousands	9 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023	Sep. 30, 2022
Supplemental disclosure of non-cash activity:
Increase in operating lease right-of-use assets	$ 4,114	$ 8,814
Increase in operating lease liabilities	4,114	9,262
Supplemental disclosure of cash activity:
Interest payments	60,715	58,405
Income tax payments	10,321	1,450
Tax refunds received	0	9,987
Reconciliation of cash, cash equivalents, and restricted cash:
Cash and cash equivalents	73,212	276,125	$ 345,590
Restricted cash	35,224	39,540	40,699
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 108,436	$ 315,665	$ 386,289	$ 251,828

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant