Segment and Geographical Area Information (Details) (Table 2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	$ 617.4	$ 569.4	$ 1,804.4	$ 1,684.1
Amortization expense	(15.1)	(14.7)	(44.8)	(49.9)
Business Combination, Acquisition and Integration Related Costs	(8.2)	(0.1)	(18.9)	(5.6)
Operating income	127.8	115.5	367.0	316.6
Nonoperating Income (Expense)	(4.7)	36.4	(18.9)	11.8
Equity in investments of unconsolidated entities	(0.1)	(2.6)	(3.9)	(5.3)
Income Loss From Continuing Operations Before Income Taxes Domestic And Foreign	123.0	149.3	344.2	323.1
Unallocated Corporate Expenses	47.1	43.5	139.0	130.4
Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	567.5	519.6	1,655.0	1,533.7
Reportable Segment Profitability	194.7	173.2	567.3	502.9
Morningstar Data and Analytics Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	93.7	91.4	277.1	269.9
PitchBook Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	52.9	50.4	158.0	137.7
Morningstar Credit Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	3.1	(0.7)	5.3	(8.5)
Morningstar Wealth Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	28.1	15.2	80.0	55.4
Morningstar Retirement Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	16.9	16.9	46.9	48.4
Corporate and Other | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	49.9	49.8	149.4	150.4
Reportable Segment Profitability	(44.1)	(42.9)	(137.9)	(130.8)
Sustainalytics
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	28.1	27.9	84.2	87.9
Morningstar Indexes [Member]
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	$ 21.8	$ 21.9	$ 65.2	$ 62.5