Property and equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2021
Property and equipment
Total property and equipment	$ 797,143	$ 708,431
Less: accumulated depreciation and amortization	(390,815)	(328,188)
Total property and equipment, net	406,328	380,243		$ 406,328
Depreciation and amortization expense
Depreciation and amortization of property and equipment	78,313	70,862	$ 78,837
Asset impairment charge
Losses on disposals of property and equipment	39		90
Construction in progress projects
Asset impairment charge
Impairment losses	23	370	$ 148
Leasehold improvements
Property and equipment
Total property and equipment	596,242	550,427
Construction in progress
Property and equipment
Total property and equipment	118,055	78,343
Software
Property and equipment
Total property and equipment	65,532	60,814
Computer equipment
Property and equipment
Total property and equipment	14,808	16,707
Furniture, fixtures and office equipment
Property and equipment
Total property and equipment	$ 2,506	$ 2,140