Property and equipment, net (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Interest cost capitalized and depreciation and amortization expense for property and equipment
Interest cost capitalized	$ 1.2	$ 0.8	$ 2.2	$ 1.7
Depreciation and amortization expense for property and equipment	$ 42.5	$ 34.4	$ 90.6	$ 67.9