Prepaid Expenses and Other (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Prepaid Expense and Other Assets [Abstract]
Prepaid expenses	$ 72.5	$ 60.3
Mobile airtime inventory	4.8	10.9
Income tax receivable	21.1	16.5
Other	20.6	15.9
Prepaid expenses and other	$ 119.0	$ 103.6