Goodwill and intangible assets Amortization expense (Details) - Minimum [Member] $ in Thousands	Dec. 31, 2015 USD ($)
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	$ 325
Finite-Lived Intangible Assets, Amortization Expense, Year Two	1,300
Finite-Lived Intangible Assets, Amortization Expense, Year Three	1,287
Finite-Lived Intangible Assets, Amortization Expense, Year Four	306
Finite-Lived Intangible Assets, Amortization Expense, Year Five	129
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	492
Finite-Lived Intangible Assets, Net	$ 3,839