CLEARING OPERATIONS - Clearing participant (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Clearing Operations
Cash Contributions	$ 2,290.1	$ 1,190.6
Non-Cash Contributions	670.8	645.9
Total Contributions	2,960.9	1,836.5
Margin deposits
Clearing Operations
Cash Contributions	1,078.7	319.5
Non-Cash Contributions	489.3	401.0
Total Contributions	1,568.0	720.5
Clearing funds
Clearing Operations
Cash Contributions	181.3	492.6
Non-Cash Contributions	51.2	69.7
Total Contributions	232.5	562.3
Interoperability funds
Clearing Operations
Cash Contributions	1,030.1	378.5
Non-Cash Contributions	130.3	175.2
Total Contributions	$ 1,160.4	$ 553.7