Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Effective tax rate	15.20%	3.40%
Effective income tax rate increase (decrease), amount	$ 350
Effective income tax rate increase (decrease), percent	11.80%
Change in valuation allowance				$ (15,400)
Forecast
Income Tax Contingency [Line Items]
Effective tax rate			40.40%