Income taxes (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax expense (benefit)	$ 12	$ 0	$ 67
Deferred tax expense (benefit)	813	277	(401)
Valuation allowance	(11,997)	(277)	334
Provision (benefit) for income taxes	$ (11,172)	$ 0	$ 0