Property and equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property and equipment
Total property and equipment	$ 306,184	$ 198,764
Less: accumulated depreciation and amortization	(113,275)	(86,992)
Total property and equipment, net	192,909	111,772
Leasehold improvements
Property and equipment
Total property and equipment	194,344	152,627
Construction in progress
Property and equipment
Total property and equipment	76,574	20,104
Computer equipment
Property and equipment
Total property and equipment	11,285	7,909
Software
Property and equipment
Total property and equipment	22,210	17,827
Furniture, fixtures and office equipment
Property and equipment
Total property and equipment	$ 1,771	$ 297