Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 48.6	$ 69.2
Restricted cash included in Current Assets	0.8	1.9
Total cash, cash equivalents, and restricted cash	49.4	71.1	$ 65.4	$ 78.0
Non-cash investing and financing activities related to property acquired under capital leases and other financing arrangements	9.6	11.5
Capital lease and deferred purchase price related to acquisitions		3.3	47.2
Accrued purchases of property and equipment	41.3	48.5	29.1
Interest payments, net of amounts capitalized and including interest on vehicle inventory financing	245.6	205.9	183.9
Income tax payments, net of income tax refunds	$ 210.0	$ 127.0	$ 265.5