v3.26.1
Intangible Assets - Schedule of Gross and Net Carrying Values of Intangible Assets (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Sep. 30, 2025
Intangible Asset, Finite-Lived, Acquired [Line Items]    
Finite-lived intangible assets, gross amount $ 475.2 $ 458.0
Finite-lived intangible assets, accumulated amortization (47.9) (26.1)
Total intangible assets subject to amortization 427.3 431.9
Indefinite-lived intangible assets 5.9 6.0
Intangible assets, gross amount 481.1 464.0
Total intangible assets, net amount 433.2 437.9
Website domains    
Intangible Asset, Finite-Lived, Acquired [Line Items]    
Indefinite-lived intangible assets 2.2 2.3
Business licenses    
Intangible Asset, Finite-Lived, Acquired [Line Items]    
Indefinite-lived intangible assets 3.7 3.7
Trade/domain names and other licenses    
Intangible Asset, Finite-Lived, Acquired [Line Items]    
Finite-lived intangible assets, gross amount 7.1 10.6
Finite-lived intangible assets, accumulated amortization (4.3) (4.9)
Total intangible assets subject to amortization 2.8 5.7
Software programs/platforms    
Intangible Asset, Finite-Lived, Acquired [Line Items]    
Finite-lived intangible assets, gross amount 2.4 2.4
Finite-lived intangible assets, accumulated amortization (2.4) (2.0)
Total intangible assets subject to amortization 0.0 0.4
Client and supplier base    
Intangible Asset, Finite-Lived, Acquired [Line Items]    
Finite-lived intangible assets, gross amount 465.7 445.0
Finite-lived intangible assets, accumulated amortization (41.2) (19.2)
Total intangible assets subject to amortization $ 424.5 $ 425.8