Restricted stock (Details Textual) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jan. 31, 2012
Shares Available for Grant, Granted			248,500
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Granted In Period Total Fair Value			$ 1,493,000
Allocated Share-based Compensation Expense	182,000	116,000	323,000	163,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	791,000		791,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized					700,000
Shares Available for Grant, Authorized	0		0			338,295
Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Forfeited In Period	6,000		8,500
Equity Incentive Plan [Member]
Shares Available for Grant, Authorized	1,038,295		1,038,295
Employees [Member]
Shares Available for Grant, Granted	4,000		140,500
Allocated Share-based Compensation Expense	89,000	63,500	155,000	93,000
Board Of Directors [Member]
Shares Available for Grant, Granted	56,000		108,000
Allocated Share-based Compensation Expense	$ 93,000		$ 168,000