Securitization - Schedule of Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Variable Interest Entity [Line Items]
Operating revenues	$ 1,962,402	$ 1,950,502	$ 3,304,987	$ 3,126,501
Operation and maintenance expense	(195,790)	(233,296)	(425,600)	(440,340)
Amortization expense	(195,687)	(182,750)	(390,332)	(363,283)
Interest expense, net	(48,731)	(50,014)	(82,144)	(102,939)
Income before income taxes	733,589	603,097	1,237,171	1,034,286
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Operating revenues	3,503	2,951	6,805	6,344
Operation and maintenance expense	(187)	(216)	(187)	(277)
Amortization expense	(2,365)	(1,689)	(4,694)	(3,953)
Interest expense, net	(951)	(1,046)	(1,924)	(2,114)
Income before income taxes	$ 0	$ 0	$ 0	$ 0

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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+ Details

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details