Regulatory Requirements and Subsidiary Dividend Restrictions - Regulatory Capital Requirements (Details)	Sep. 30, 2022 USD ($)
StoneX Financial Inc.
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	$ 6,278,600,000
Secured funds	212,400,000
Minimum regulatory requirement	6,206,700,000
Secured funds required under commodity exchange act	199,400,000
StoneX Financial Ltd.
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	1,242,400,000
Minimum regulatory requirement	1,244,100,000
StoneX Financial Pte. Ltd.
Capital and Other Regulatory Requirements [Line Items]
Cash and securities segregated under commodity exchange act regulation	556,800,000
Minimum regulatory requirement	538,900,000
StoneX Markets LLC
Capital and Other Regulatory Requirements [Line Items]
Minimum regulatory capital requirement	$ 20,000,000