Stock incentive plan (Details) (USD $)
 3 Months Ended 9 Months Ended
Mar. 31, 2009
Sep. 30, 2012
Sep. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized for issuance (in shares)   455,000  
Options [Roll Forward]      
Options outstanding, beginning of period (in shares)   264,980 310,205
Granted (in shares)   5,000 0
Forfeited (in shares)   (3,450) 0
Exercised (in shares)   0 0
Options outstanding, end of period (in shares)   266,530 310,205
Options exercisable end of period (in shares)   261,530 291,350
Weighted Average Exercise Price [Roll Forward]      
Options outstanding, beginning of period (in dollars per share)   $ 9.48 $ 9.48
Granted (in dollars per share)   $ 0 $ 0
Forfeited (in dollars per share)   $ 4.98 $ 0
Exercised (in dollars per share)   $ 0 $ 0
Options outstanding, end of period (in dollars per share)   $ 9.54 $ 9.48
Options outstanding, fair value per share [Abstract]      
Options outstanding, beginning of the period, fair value (in dollars per share)   $ 4.70 $ 4.73
Granted (in dollars per share)   $ 0 $ 0
Forfeited (in dollars per share)   $ 3.12 $ 0
Exercised (in dollars per share)   $ 0 $ 0
Options outstanding, ending balance fair value (in dollars per share)   $ 4.66 $ 4.73
Options outstanding, end of period, intrinsic value   $ 0 $ 0
Number of shares of common stocks issued at grant date (in shares) 26,592    
Weighted average fair market value at date of grant (in dollars per share) $ 4.60    
Non-vested restricted stock and performance award (in shares)     6,271
Unamortized stock-based compensation related to nonvested share based compensation arrangements   2,734 35,960
Weighed average period of time based unamortized compensation, recognition   2 years 9 months 29 days  
Stock-based compensation expense   $ 6,506 $ 88,835