v3.26.3
REVENUE RECOGNITION - Disaggregation of Operating Revenue (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Disaggregation Of Revenue [Line Items]        
Operating revenues $ 892.0 $ 793.4 $ 2,609.8 $ 2,311.9
Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 532.6 451.1 1,539.9 1,307.7
Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 191.0 182.2 570.4 532.1
Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 93.7 90.1 277.5 263.6
All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues 74.7 70.0 222.0 208.5
Recurring subscriptions        
Disaggregation Of Revenue [Line Items]        
Operating revenues 623.6 579.1 1,837.2 1,694.4
Recurring subscriptions | Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 269.5 242.5 786.7 711.5
Recurring subscriptions | Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 188.1 178.3 557.2 517.8
Recurring subscriptions | Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 92.2 88.7 273.6 258.4
Recurring subscriptions | All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues 73.8 69.6 219.7 206.7
Asset-based fees        
Disaggregation Of Revenue [Line Items]        
Operating revenues 246.6 197.5 704.2 559.0
Asset-based fees | Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 246.6 197.5 704.2 559.0
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 21.8 16.8 68.4 58.5
Non-recurring | Index        
Disaggregation Of Revenue [Line Items]        
Operating revenues 16.5 11.1 49.0 37.2
Non-recurring | Analytics        
Disaggregation Of Revenue [Line Items]        
Operating revenues 2.9 3.9 13.2 14.3
Non-recurring | Sustainability and Climate        
Disaggregation Of Revenue [Line Items]        
Operating revenues 1.5 1.4 3.9 5.2
Non-recurring | All Other - Private Assets        
Disaggregation Of Revenue [Line Items]        
Operating revenues $ 0.9 $ 0.4 $ 2.3 $ 1.8