Property and Equipment, net - Interest Cost Capitalized and Depreciation and Amortization Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Interest cost capitalized	$ 1.3	$ 1.8	$ 5.0	$ 7.8
Depreciation and amortization expense for property and equipment	$ 29.0	$ 27.3	$ 87.6	$ 75.9