Earnings Per Share - Level 4 Tag - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net Income
Income from continuing operations	$ 70.0	$ 107.0	$ 144.3	$ 181.9
Less: net income attributable to the noncontrolling interests	(1.5)	(2.5)	(5.6)	(4.9)
Income from continuing operations attributable to TransUnion	68.5	104.5	138.7	177.0
Discontinued operations, net of tax	0.0	(3.0)	0.0	(4.6)
Net income attributable to TransUnion	$ 68.5	$ 101.5	$ 138.7	$ 172.4
Basic earnings per common share from:
Income from continuing operations attributable to TransUnion	$ 0.36	$ 0.56	$ 0.73	$ 0.95
Discontinued operations, net of tax	0	(0.02)	0	(0.02)
Net Income attributable to TransUnion common stockholders, Basic	0.36	0.54	0.73	0.92
Diluted earnings per common share from:
Income from continuing operations attributable to TransUnion	0.36	0.55	0.72	0.93
Discontinued operations, net of tax	0	(0.02)	0	(0.02)
Net Income attributable to TransUnion common stockholders, Diluted	$ 0.36	$ 0.53	$ 0.72	$ 0.90
Weighted Average Number of Shares Outstanding, Basic	189,900,000	187,500,000	189,600,000	187,100,000
Weighted Average Number Diluted Shares Outstanding Adjustment	2,100,000	3,800,000	2,500,000	4,100,000
Weighted Average Number of Shares Outstanding, Diluted	192,000,000.0	191,300,000	192,000,000.0	191,200,000
Performance Shares Contingency Not Met [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			1,300,000	1,100,000
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.3	0	0.3	0.1