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Income Taxes Income Tax Rate Reconciliation (Details)	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%	21.00%
Adjustments to reconcile to the effective tax rate:
State income taxes, net of federal benefit	3.90%	3.40%	3.90%	3.40%
Tax benefits from stock compensation	(1.00%)	0.00%	(2.00%)	0.10%
Tax credits	(1.60%)	(2.10%)	(1.60%)	(2.10%)
Effective Income Tax Rate Reconciliation, GILTI, percent	0.30%	0.20%	0.30%	0.20%
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent	(0.40%)	(0.80%)	(0.40%)	(0.80%)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-Based Payment Arrangement, Percent	1.40%	1.00%	1.40%	1.00%
Effective Income Tax Rate Reconciliation, Uncertain Tax Positions	0.30%	0.50%	0.50%	(1.60%)
Valuation allowance adjustment related to stock compensation	0.00%	0.00%	0.10%	0.00%
Other	0.30%	1.60%	0.50%	1.50%
Effective income tax rate	24.20%	24.80%	23.70%	22.70%

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Effective Income Tax Rate Reconciliation, Uncertain Tax Positions

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of reported income tax benefit (expense) from difference to income tax expense (benefit) computed by applying statutory federal (national) income tax rate to pretax income (loss) from continuing operation, attributable to other reconciling items. Excludes state and local income tax expense (benefit), federal tax expense (benefit), statutory income tax expense (benefit) outside of country of domicile, tax credit, nondeductible expense, deduction, income tax settlement, income tax contingency, and cross-border tax law.

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