Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Income
Income from continuing operations	$ 106.7	$ 88.3	$ 251.0	$ 270.2
Less: net income attributable to the noncontrolling interests	(3.9)	3.4	(9.5)	(1.5)
Income from continuing operations attributable to TransUnion	102.8	91.7	241.5	268.7
Discontinued operations, net of tax	0.0	0.0	0.0	(4.6)
Net income attributable to TransUnion	$ 102.8	$ 91.7	$ 241.5	$ 264.1
Basic earnings per common share from:
Income from continuing operations attributable to TransUnion	$ 0.54	$ 0.49	$ 1.27	$ 1.43
Discontinued operations, net of tax	0	0	0	(0.02)
Net Income attributable to TransUnion common stockholders, Basic	0.54	0.49	1.27	1.41
Diluted earnings per common share from:
Income from continuing operations attributable to TransUnion	0.53	0.48	1.26	1.40
Discontinued operations, net of tax	0	0	0	(0.02)
Net Income attributable to TransUnion common stockholders, Diluted	$ 0.53	$ 0.48	$ 1.26	$ 1.38
Weighted Average Number of Shares Outstanding, Basic	190.2	188.2	189.8	187.5
Weighted Average Number Diluted Shares Outstanding Adjustment	2.1	3.8	2.3	4.1
Weighted Average Number of Shares Outstanding, Diluted	192.3	192.0	192.1	191.6
Performance Shares Contingency Not Met [Member]
Diluted earnings per common share from:
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			1.3	1.1
Performance Shares [Member]
Diluted earnings per common share from:
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.1	0.1	0.3	0.2