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

Morningstar, Inc. 10-Q