Supplemental Cash Flow Information Significant Non-Cash Investing Activities (Details) £ in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017 GBP (£) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)
Outstanding receivables from outside parties for the funding of capital expenditures		$ 19.4		$ 10.7	$ 17.7
Purchases of property and equipment accrued in accounts payable		$ 26.9	$ 20.0	$ 16.4
Common Stock [Member] | Class A Common Stock [Member]
Stock issued during period, shares | shares			238,201
Settlement of Freightliner Deferred Consideration [Member]
Notes Payable	£ 6.3				8.4
Notes Payable, Fair Value Disclosure	£ 5.7				$ 7.5
Settlement of Freightliner Deferred Consideration [Member] | Common Stock [Member] | Class A Common Stock [Member]
Stock issued during period, shares | shares	238,201
Settlement of Freightliner Deferred Consideration [Member] | Additional Paid-in Capital [Member]
Conversion of Stock, Amount Issued			$ 17.5