Segment and Geographical Area Information (Details) (Table 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	$ 31.9	$ 30.9	$ 97.9	$ 91.6
Stock-based compensation expense			46.1	38.8
Operating Segments
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	27.6	26.1	83.7	78.2
Operating Segments | Morningstar Data and Analytics Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	11.3	9.8	33.3	27.5
Operating Segments | PitchBook Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	8.7	7.6	24.6	23.3
Operating Segments | Morningstar Credit Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	3.0	4.3	11.9	14.0
Operating Segments | Morningstar Wealth Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	2.0	2.2	6.0	5.8
Operating Segments | Morningstar Retirement Segment
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	2.6	2.2	7.9	7.6
Operating Segments | Corporate and Other
Segment, Reconciliation of Other Items from Segments to Consolidated [Line Items]
Depreciation	$ 4.3	$ 4.8	$ 14.2	$ 13.4