Segment and Geographical Area Information (Details) (Table 2) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	$ 581.9	$ 542.8
Amortization expense	(14.4)	(17.7)
Business Combination, Acquisition and Integration Related Costs	(6.9)	(0.5)
Operating income	114.1	92.6
Nonoperating Income (Expense)	(5.6)	(5.6)
Equity in investments of unconsolidated entities	(2.6)	(1.5)
Income Loss From Continuing Operations Before Income Taxes Domestic And Foreign	105.9	85.5
Unallocated Corporate Expenses	41.8	40.9
Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	530.1	492.0
Reportable Segment Profitability	174.6	152.1
Morningstar Data and Analytics Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	87.1	91.2
PitchBook Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	52.3	40.0
Morningstar Credit Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	(0.8)	(5.6)
Morningstar Wealth Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	21.4	12.3
Morningstar Retirement Segment | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Reportable Segment Profitability	14.6	14.2
Corporate and Other | Operating Segments
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	51.8	50.8
Reportable Segment Profitability	(39.2)	(41.3)
Sustainalytics
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	28.8	30.8
Morningstar Indexes [Member]
Reconciliation of Select Segment Information to Consolidated [Line Items]
Revenue	$ 23.0	$ 20.0