Annual report [Section 13 and 15(d), not S-K Item 405]

Income Taxes - Reconciliation of Tax Provision Using the Federal Statutory Income Tax Rate to Reported Provision (Details)

v3.25.3
Income Taxes - Reconciliation of Tax Provision Using the Federal Statutory Income Tax Rate to Reported Provision (Details) - USD ($)
$ in Thousands
12 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2023
Reconciliation of actual provision for income taxes and provision for income taxes resulting from the use of federal statutory income tax      
Tax expense at statutory rate $ 93,418 $ 85,367 $ 44,162
State income taxes, net of federal benefit 24,203 21,582 11,501
Foreign taxation rate differentials 80 875 (590)
Non-deductible expenses 4,147 2,444 2,889
Global intangible low taxed income 750 1,257 2,274
Valuation allowance - foreign jurisdictions 0 734 2,010
Tax credits (6,384) (8,997) (6,645)
Divestiture-related charges 8,379 0 0
Excess tax expense/(benefits) from stock-based compensation (1,546) (1,656) (1,399)
Other 2,768 (2,011) (5,701)
Income tax expense $ 125,815 $ 99,595 $ 48,501
Effective Income Tax Rate Reconciliation, Percent [Abstract]      
U.S Federal Statutory tax rate (as percent) 21.00% 21.00% 21.00%
State income taxes, net of federal benefit 5.40% 5.30% 5.50%
Foreign taxation rate differentials 0.00% 0.20% (0.30%)
Non-deductible expenses 0.90% 0.60% 1.40%
Global intangible low taxed income 0.20% 0.30% 1.10%
Valuation allowance - foreign jurisdictions 0.00% 0.20% 1.00%
Tax credits (1.40%) (2.20%) (3.20%)
Divestiture-related charges 1.90% 0.00% 0.00%
Excess tax expense/(benefits) from stock-based compensation (0.30%) (0.40%) (0.70%)
Other 0.60% (0.50%) (2.70%)
Effective tax rate (as percent) 28.30% 24.50% 23.10%