Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Supplemental Cash Flow Information [Abstract]
Capital lease and deferred purchase price related to acquisitions	$ 3.3
Non-cash investing and financing activities related to property acquired under capital leases	7.7	$ 36.3
Accrued purchases of property and equipment	22.7	14.5
Interest payments, net of amounts capitalized and including interest on vehicle inventory financing	148.6	133.0
Income tax payments, net of income tax refunds	$ 126.3	$ 193.3