Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Trade accounts payable	$ 204.9	$ 157.7
Employee-related expenses	59.7	28.1
Accrued vacation	23.8	21.8
Miscellaneous accrued expenses	87.4	113.6
Total accounts payable and accrued expenses	$ 375.8	$ 321.2