Time deposits (Narrative) (Details) (USD $)
Dec. 31, 2014
Dec. 31, 2013
Time Deposits, Type [Line Items]    
Time Deposits, $100,000 or More $ 113,700,000 $ 92,700,000
Wholesale Brokered Time Deposits    
Time Deposits, Type [Line Items]    
Time Deposits $ 0 $ 0