Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	15	9
Earnings Per Share, Basic [Abstract]
Net income attributable to Morningstar, Inc.	$ 26,376	$ 29,618
Less: Distributed Earnings Available to Participating Securities	(3)	(15)
Less: Undistributed earnings allocated to participating securities	(7)	(13)
Numerator for basic net income per share - undistributed and distributed earnings available to common shareholders	26,366	29,590
Weighted average common shares outstanding	44,777	46,406
Basic net income per share attributable to Morningstar, Inc.	$ 0.59	$ 0.64
Earnings Per Share, Diluted [Abstract]
Numerator for basic net income per share - undistributed and distributed earnings available to common shareholders	26,366	29,590
Add: Undistributed Earnings Allocated To Participating Securities	7	13
Less: Undistributed Earnings Reallocated to Participating Securities	(7)	(13)
Numerator for diluted net income per share - undistributed and distributed earnings available to common shareholders	$ 26,366	$ 29,590
Weighted average common shares outstanding	44,777	46,406
Net effect of dilutive stock options and restricted stock units	316	408
Weighted average common shares outstanding for computing diluted income per share	45,093	46,814
Diluted net income per share attributable to Morningstar, Inc.	$ 0.58	$ 0.63
Stock Options [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0
Restricted Stock Units (RSUs) [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	6	9
Performance Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	9	0
Restricted Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0