Segment and Geographical Area Information (Details) (Table 3) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	$ 33.2	$ 31.5	$ 66.0	$ 60.7
Stock-based compensation expense			27.5	25.6
Operating Segments
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	28.4	27.1	56.1	52.1
Operating Segments \| Morningstar Data and Analytics Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	11.2	9.5	22.0	17.7
Operating Segments \| PitchBook Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	8.1	8.3	15.9	15.7
Operating Segments \| Morningstar Credit Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	4.4	5.0	8.9	9.7
Operating Segments \| Morningstar Wealth Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	2.0	1.7	4.0	3.6
Operating Segments \| Morningstar Retirement Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	2.7	2.6	5.3	5.4
Operating Segments \| Corporate and Other
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	$ 4.8	$ 4.4	$ 9.9	$ 8.6