Commitments and contingencies (Details) (USD $)
9 Months Ended
Sep. 30, 2012
Dec. 31, 2011
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Total commitments to extend credit $ 73,555,000 $ 62,594,000
Number of days from effective date of order to retain qualified management 90 days  
Number of days from effective date to retain bank consultant to develop management's report 30 days  
Number of days from receipt of consultant's report to formulate written management's plan 30 days  
Number of days from effective date of order for Tier 1 capital and total risk-based capital requirement 90 days  
Tier One Risk Based Capital requirement (in hundredths) 8.00%  
Capital required for capital adequacy to risk weighted assets (in hundredths) 11.00%  
Number of days from effective date of order to submit written capital plan to Supervisory Authorities 90 days  
Policy for chargeoffs The Order requires the Bank to eliminate from its books, by charge-off or collection, all assets or portions of assets classified "Loss" and 50 percent of those classified "Doubtful". If an asset is classified "Doubtful", the Bank may, in the alternative, charge off the amount that is considered uncollectible in accordance with the Bank's written analysis of loan or lease impairment.  
Number of days required to notify Supervisory Authorities prior to undertaking asset growth 60 days  
Percentage of asset growth (in hundredths) 10.00%  
Undisbursed credit lines [Member]
   
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Total commitments to extend credit 34,947,000 40,661,000
Commitments to extend credit or originate credit [Member]
   
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Total commitments to extend credit 35,834,000 18,214,000
Standby letters of credit [Member]
   
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]    
Total commitments to extend credit $ 2,774,000 $ 3,719,000