Stock repurchase (Details) (USD $)	Dec. 31, 2013
Stock repurchase
Authorized shares of "blank check" preferred stock	4,000,000
Authorized shares of 6% Senior Convertible Preferred Stock	1,500,000
Authorized shares of Series A Participating Preferred Stock	100,000
Company had repurchased an aggregate of shares	172,603
Company had repurchased an aggregate value of shares	$ 403,000