Loss Per Common Share (Details) - shares
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Common shares      
Shares with anti-dilutive effect, not included in calculation of earnings per share 5,033,156 3,411,270 1,698,569
Convertible Preferred Stock      
Shares with anti-dilutive effect, not included in calculation of earnings per share 4,566,836 5,935,000 6,522,556