Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits - beginning balance	$ 57,797	$ 58,638	$ 52,683
Decrease resulting from prior period tax positions	(1,759)	(2,867)	(631)
Decrease resulting from a lapse in statute of limitations	(5,699)	(6,188)	0
Increase resulting from current period tax positions	9,993	8,214	6,586
Unrecognized tax benefits - ending balance	60,332	57,797	58,638
Less: deferred federal and state income tax benefits	(12,670)	(12,137)	(12,314)
Total unrecognized tax benefits that, if recognized, would impact the effective income tax rate as of the end of the year	47,662	$ 45,660	$ 46,324
Anticipated regulatory offset	$ 43,300

Amount of deferred federal and state income tax benefits pertaining to unrecognized tax benefits.

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- Definition

The amount that will be offset against future earnings by anticipated increases or decreases in other expenses or revenues.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of unrecognized tax benefits.

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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