Label	Element	Value
Cash Segregated under Commodity Exchange Act Regulation	us-gaap_CashSegregatedUnderCommodityExchangeActRegulation	$ 2,000,300,000	[1]
Cash Segregated under Commodity Exchange Act Regulation	us-gaap_CashSegregatedUnderCommodityExchangeActRegulation	1,168,000,000.0	[1]
Securities Segregated under Other Regulations	us-gaap_SecuritiesSegregatedUnderOtherRegulations	100,000,000.0	[2]
Securities Segregated under Other Regulations	us-gaap_SecuritiesSegregatedUnderOtherRegulations	106,200,000	[2]
Non-cash equivalent segregated assets	intl_Noncashequivalentsegregatedassets	8,100,000
Non-cash equivalent segregated assets	intl_Noncashequivalentsegregatedassets	102,600,000
Cash Segregated And Deposited With Or Pledged To Exchange-clearing Organizations And Other Futures Commission Merchants	intl_CashSegregatedAndDepositedWithOrPledgedToExchangeClearingOrganizationsAndOtherFuturesCommissionMerchants	1,896,700,000	[2]
Cash Segregated And Deposited With Or Pledged To Exchange-clearing Organizations And Other Futures Commission Merchants	intl_CashSegregatedAndDepositedWithOrPledgedToExchangeClearingOrganizationsAndOtherFuturesCommissionMerchants	$ 2,050,300,000	[2]
Accounting Standards Update [Extensible List]	us-gaap_AccountingStandardsUpdateExtensibleList	us-gaap:AccountingStandardsUpdate201802Member
Non-segregated cash and other non-cash equivalent assets included within deposits and receivables from broker-dealers, clearing organizations, and counterparties	intl_Nonsegregatedcashandothernoncashequivalentassetsincludedwithindepositsandreceivablesfrombrokerdealersclearingorganizationsandcounterparties	$ 1,356,600,000
Non-segregated cash and other non-cash equivalent assets included within deposits and receivables from broker-dealers, clearing organizations, and counterparties	intl_Nonsegregatedcashandothernoncashequivalentassetsincludedwithindepositsandreceivablesfrombrokerdealersclearingorganizationsandcounterparties	$ 2,210,900,000

[1] (1) Represents segregated client cash and United States (“U.S.”) Treasury obligations held at third-party banks. Excludes segregated commodity warehouse receipts, segregated U.S. Treasury obligations with original or acquired maturities of greater than 90 days, and other assets of $102.6 million and $8.1 million as of March 31, 2021 and 2020, respectively, included within ‘Cash, securities and other assets segregated under federal and other regulations’ on the condensed consolidated balance sheets.

[2] (2) Represents segregated client cash and U.S. Treasury obligations on deposit with, or pledged to, exchange clearing organizations and other FCMs. Excludes non-segregated cash, segregated U.S. Treasury obligations pledged to exchange-clearing organizations with original or acquired maturities greater than 90 days, and other assets of $2,210.9 million and $1,356.6 million as of March 31, 2021 and 2020, respectively, included within ‘Deposits with and receivables from broker-dealers, clearing organizations, and counterparties, net’ on the condensed consolidated balance sheets.