v3.26.1
REVENUE RECOGNITION - Disaggregation of Operating Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Disaggregation Of Revenue [Line Items]        
Operating revenues $ 867.0 $ 772.7 $ 1,717.8 $ 1,518.5
Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 511.0 434.9 1,007.3 856.6
Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 189.4 177.7 379.4 349.9
Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 91.9 88.9 183.8 173.5
All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues 74.7 71.2 147.3 138.5
Recurring subscriptions        
Disaggregation Of Revenue [Line Items]        
Operating revenues 613.4 562.8 1,213.6 1,115.3
Recurring subscriptions | Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 263.0 235.7 517.2 469.0
Recurring subscriptions | Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 185.9 169.8 369.1 339.5
Recurring subscriptions | Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 90.5 87.0 181.4 169.7
Recurring subscriptions | All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues 74.0 70.3 145.9 137.1
Asset-based fees        
Disaggregation Of Revenue [Line Items]        
Operating revenues 233.1 184.1 457.6 361.5
Asset-based fees | Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 233.1 184.1 457.6 361.5
Asset-based fees | Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 0.0 0.0 0.0 0.0
Asset-based fees | Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 0.0 0.0 0.0 0.0
Asset-based fees | All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues 0.0 0.0 0.0 0.0
Non-recurring        
Disaggregation Of Revenue [Line Items]        
Operating revenues 20.5 25.8 46.6 41.7
Non-recurring | Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 14.9 15.1 32.5 26.1
Non-recurring | Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 3.5 7.9 10.3 10.4
Non-recurring | Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 1.4 1.9 2.4 3.8
Non-recurring | All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues $ 0.7 $ 0.9 $ 1.4 $ 1.4