Loans and allowance for loan losses (Details 6)
$ in Thousands
3 Months Ended
Mar. 31, 2016
USD ($)
Loans
Loan
Mar. 31, 2015
USD ($)
Loans
Loan
Defaults on TDRs [Line Items]    
Number of Loans | Loan 5 2
Recorded Balance $ 562 $ 527
Commercial Real Estate [Member]    
Defaults on TDRs [Line Items]    
Number of Loans | Loan 0 1
Recorded Balance $ 0 $ 406
Owner Occupied [Member]    
Defaults on TDRs [Line Items]    
Number of Loans | Loans 0 1
Recorded Balance $ 0 $ 406
Consumer Real Estate [Member]    
Defaults on TDRs [Line Items]    
Number of Loans | Loan 4 1
Recorded Balance $ 443 $ 121
First Deed of Trust [Member]    
Defaults on TDRs [Line Items]    
Number of Loans | Loans 1 1
Recorded Balance $ 262 $ 121
Second Deed of Trust [Member]    
Defaults on TDRs [Line Items]    
Number of Loans | Loans 3 0
Recorded Balance $ 181 $ 0
Commercial and industrial loans (except those secured by real estate) [Member]    
Defaults on TDRs [Line Items]    
Number of Loans | Loans 1 0
Recorded Balance $ 119 $ 0