Property and Equipment, net Property Plant and Equipment Income Statement Disclosures - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Interest cost capitalized	$ 1.5	$ 3.0	$ 3.7	$ 6.0
Depreciation and amortization expense for property and equipment	$ 29.7	$ 24.5	$ 58.6	$ 48.6