Cash Flow Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	$ 72.0		$ 569.6
Restricted cash included in Other Current Assets	0.1		0.1
Total cash, cash equivalents, and restricted cash	72.1	$ 350.6	$ 569.7	$ 42.5
Accrued purchases of property and equipment	14.5	8.1
Non-cash investing and financing activities related to property acquired under other financing arrangements		0.9
Adjustments to right-of use assets including right-of-use assets obtained in exchange for new operating lease liabilities	5.7	26.4
Adjustments to right-of use assets including right-of-use assets obtained in exchange for new finance lease liabilities	63.3	34.0
Interest payments, net of amounts capitalized and including interest on vehicle inventory financing	71.1	108.7
Income tax payments, net of income tax refunds	$ 331.5	$ 116.0