SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)
Summary of Significant Accounting Policies
Number of reportable segments | segment	5	6
Revenues	$ 4,714.2	$ 4,094.5	$ 3,773.5
Options to renew	true
Option to terminate period (in years)	1 year
Minimum
Summary of Significant Accounting Policies
Useful life (in years)	3 years
Renewal term (in years)	1 year
Maximum
Summary of Significant Accounting Policies
Useful life (in years)	7 years
Renewal term (in years)	5 years
Option to terminate period (in years)	1 year
Revenue from Contract with Customer Benchmark | Customer Concentration Risk | Major Customer
Summary of Significant Accounting Policies
Concentration risk (as a percent)	10.00%	10.00%	10.00%
Revenues	$ 480.0	$ 403.1	$ 389.4
Market-Maker Transaction Benchmark | Customer Concentration Risk | Three Largest Clearing Members
Summary of Significant Accounting Policies
Concentration risk (as a percent)	71.00%