v3.26.1
Acquisitions, Goodwill and Other Intangible Assets (Schedule of Goodwill) (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Business Combination [Line Items]    
Goodwill $ 1,747.2  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 1,610.8  
Foreign currency translation and other (3.2)  
Goodwill, Ending Balance 1,747.2  
Operating Segments    
Business Combination [Line Items]    
Goodwill 1,537.6  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 1,540.7  
Foreign currency translation and other (3.1)  
Goodwill, Ending Balance 1,537.6  
Morningstar Data and Analytics Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill 605.3  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 608.6  
Foreign currency translation and other (3.3)  
Goodwill, Ending Balance 605.3  
PitchBook Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill 628.7  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 628.7  
Foreign currency translation and other 0.0  
Goodwill, Ending Balance 628.7  
Morningstar Credit Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill 118.7  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 119.6  
Foreign currency translation and other (0.9)  
Goodwill, Ending Balance 118.7  
Morningstar Wealth Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill 91.4  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 90.3  
Foreign currency translation and other 1.1  
Goodwill, Ending Balance 91.4  
Morningstar Retirement Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill 93.5  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 93.5  
Foreign currency translation and other 0.0  
Goodwill, Ending Balance 93.5  
Corporate and Other | Operating Segments    
Business Combination [Line Items]    
Goodwill 209.6  
Goodwill [Roll Forward]    
Goodwill, Beginning Balance 70.1  
Foreign currency translation and other (0.1)  
Goodwill, Ending Balance 209.6  
DealX    
Business Combination [Line Items]    
Goodwill, Acquired During Period 139.6 $ 9.7
DealX | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period 0.0  
DealX | Morningstar Data and Analytics Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period 0.0  
DealX | PitchBook Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period 0.0  
DealX | Morningstar Credit Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period 0.0  
DealX | Morningstar Wealth Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period 0.0  
DealX | Morningstar Retirement Segment | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period 0.0  
DealX | Corporate and Other | Operating Segments    
Business Combination [Line Items]    
Goodwill, Acquired During Period $ 139.6  
Lumonic    
Business Combination [Line Items]    
Goodwill, Acquired During Period   $ 21.3