v3.26.1
Goodwill and Intangible Assets - Schedule of Goodwill and Acquired Intangible Assets (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Sep. 30, 2025
Intangible Asset, Finite-Lived [Line Items]    
Goodwill (not amortized) $ 3,398,303 $ 3,493,316
Intangible assets with finite lives (amortized), Gross Carrying Amount 1,694,193 1,853,441
Intangible assets with finite lives (amortized), Accumulated Amortization 928,394 1,028,778
Intangible assets with finite lives (amortized), Net Book Value 765,799 824,663
Intangible Assets, Net (Including Goodwill) 4,164,102 4,317,979
Purchased software    
Intangible Asset, Finite-Lived [Line Items]    
Intangible assets with finite lives (amortized), Gross Carrying Amount 547,640 639,104
Intangible assets with finite lives (amortized), Accumulated Amortization 401,974 472,357
Intangible assets with finite lives (amortized), Net Book Value 145,666 166,747
Capitalized Software    
Intangible Asset, Finite-Lived [Line Items]    
Intangible assets with finite lives (amortized), Gross Carrying Amount 22,877 22,877
Intangible assets with finite lives (amortized), Accumulated Amortization 22,877 22,877
Intangible assets with finite lives (amortized), Net Book Value 0 0
Customer Lists and Relationships    
Intangible Asset, Finite-Lived [Line Items]    
Intangible assets with finite lives (amortized), Gross Carrying Amount 1,088,385 1,149,262
Intangible assets with finite lives (amortized), Accumulated Amortization 480,308 505,202
Intangible assets with finite lives (amortized), Net Book Value 608,077 644,060
Trademarks and Trade Names    
Intangible Asset, Finite-Lived [Line Items]    
Intangible assets with finite lives (amortized), Gross Carrying Amount 31,822 38,179
Intangible assets with finite lives (amortized), Accumulated Amortization 19,766 24,323
Intangible assets with finite lives (amortized), Net Book Value 12,056 13,856
Other    
Intangible Asset, Finite-Lived [Line Items]    
Intangible assets with finite lives (amortized), Gross Carrying Amount 3,469 4,019
Intangible assets with finite lives (amortized), Accumulated Amortization 3,469 4,019
Intangible assets with finite lives (amortized), Net Book Value $ 0 $ 0