Property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 9,288	$ 4,018
Less: accumulated depreciation	(1,395)	(784)
Property and equipment, net	7,893	3,234
Depreciation expense	612	600	$ 184
Construction in progress	3,000
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,341	1,336
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	526	$ 499
Construction in progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,873
Other.
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 242