- Components of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net earnings from continuing operations attributable to CDK	$ 68.0	$ 70.7	$ 144.3	$ 145.2
(Loss) Earnings from discontinued operations, net of taxes	(45.7)	18.3	(40.0)	34.1
Net earnings attributable to CDK	$ 22.3	$ 89.0	$ 104.3	$ 179.3
Weighted-average shares outstanding:
Basic (shares)	121.6	126.8	121.5	128.2
Effect of employee stock options (shares)	0.1	0.2	0.1	0.2
Effect of employee restricted stock (shares)	0.4	0.5	0.5	0.7
Diluted (shares)	122.1	127.5	122.1	129.1
Net earnings (loss) attributable to CDK per share - basic:
Continuing operations (in dollars per share)	$ 0.56	$ 0.56	$ 1.19	$ 1.13
Discontinued operations (in dollars per share)	(0.38)	0.14	(0.33)	0.27
Total net earnings attributable to CDK per share - basic (in dollars per share)	0.18	0.70	0.86	1.40
Net earnings (loss) attributable to CDK per share - diluted:
Continuing operations (in dollars per share)	0.55	0.56	1.18	1.13
Discontinued operations (in dollars per share)	(0.37)	0.14	(0.33)	0.26
Total net earnings attributable to CDK per share - diluted (in dollars per share)	$ 0.18	$ 0.70	$ 0.85	$ 1.39