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Financial Data by Segment - Revenue and Earnings Before Taxes by Segment (Details) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) operating_segment reportable_segment	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments \| operating_segment			2
Number of reportable segments \| reportable_segment			2
Revenues	$ 499.6	$ 478.7	$ 994.2	$ 925.0
Earnings before income taxes	113.0	96.6	217.0	203.1
Other
Segment Reporting Information [Line Items]
Earnings before income taxes	(54.7)	(60.3)	(110.1)	(131.1)
CDK North America
Segment Reporting Information [Line Items]
Revenues	418.2	406.7	835.9	774.4
CDK North America \| Operating Segments
Segment Reporting Information [Line Items]
Earnings before income taxes	151.8	147.4	296.0	305.9
CDKI
Segment Reporting Information [Line Items]
Revenues	81.4	72.0	158.3	150.6
CDKI \| Operating Segments
Segment Reporting Information [Line Items]
Earnings before income taxes	15.9	9.5	31.1	28.3
Subscription \| CDK North America
Segment Reporting Information [Line Items]
Revenues	336.8	330.0	669.2	630.9
Subscription \| CDKI
Segment Reporting Information [Line Items]
Revenues	68.2	61.2	135.9	127.8
On-site licenses and installation \| CDK North America
Segment Reporting Information [Line Items]
Revenues	3.0	2.8	5.1	4.2
On-site licenses and installation \| CDKI
Segment Reporting Information [Line Items]
Revenues	8.8	7.5	13.3	15.5
Transaction \| CDK North America
Segment Reporting Information [Line Items]
Revenues	39.8	38.3	82.5	79.3
Other \| CDK North America
Segment Reporting Information [Line Items]
Revenues	38.6	35.6	79.1	60.0
Other \| CDKI
Segment Reporting Information [Line Items]
Revenues	$ 4.4	$ 3.3	$ 9.1	$ 7.3