Property and equipment - Summary by type (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property and equipment
Total property and equipment	$ 408,592	$ 337,888
Less: accumulated depreciation and amortization	(158,281)	(123,388)
Total property and equipment, net	250,311	214,500
Leasehold improvements
Property and equipment
Total property and equipment	345,249	243,743
Construction in progress
Property and equipment
Total property and equipment	19,460	57,692
Software
Property and equipment
Total property and equipment	31,376	24,349
Computer equipment
Property and equipment
Total property and equipment	10,757	10,366
Furniture, fixtures and office equipment
Property and equipment
Total property and equipment	$ 1,750	$ 1,738