Interim Financial Data by Segment - Revenue and Earnings Before Taxes by Segment (Details) (USD $)
3 Months Ended 9 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2015
Mar. 31, 2014
Segment Reporting Information [Line Items]        
Amortization of intangibles $ 7,000,000 $ 7,100,000 $ 37,500,000 $ 21,500,000
Revenues 526,400,000 501,100,000 1,560,400,000 1,470,900,000
Earnings before Income Taxes 91,000,000 100,500,000 232,600,000 268,100,000
Separation costs 600,000 0 34,600,000 0
Segment Reconciling Items        
Segment Reporting Information [Line Items]        
Revenues (14,700,000) (1,500,000) (23,500,000) (5,400,000)
Earnings before Income Taxes (2,400,000) (200,000) (4,100,000) 300,000
Automotive Retail North America | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 347,300,000 321,500,000 1,007,000,000 948,500,000
Earnings before Income Taxes 103,200,000 100,300,000 290,400,000 264,700,000
Automotive Retail International | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 87,600,000 85,200,000 261,700,000 255,200,000
Earnings before Income Taxes 13,000,000 12,500,000 41,500,000 37,000,000
Other        
Segment Reporting Information [Line Items]        
Separation costs 600,000 0 34,600,000 0
Other | Operating Segments        
Segment Reporting Information [Line Items]        
Earnings before Income Taxes (33,700,000) (17,700,000) (110,100,000) (51,600,000)
Digital Marketing        
Segment Reporting Information [Line Items]        
Amortization of intangibles     15,600,000  
Digital Marketing | Operating Segments        
Segment Reporting Information [Line Items]        
Revenues 106,200,000 95,900,000 315,200,000 272,600,000
Earnings before Income Taxes $ 10,900,000 $ 5,600,000 $ 14,900,000 $ 17,700,000