Share Capital (Details Textual)	Mar. 31, 2018 vote shares	Dec. 31, 2017 shares
Preferred Stock | Series 4 Convertible Preferred Stock
Share Capital [Line Items]
Shares outstanding (shares)	95,000	95,000
Common Stock
Share Capital [Line Items]
Shares outstanding (shares)	56,436,067	56,375,131
Common Stock | Common Class A
Share Capital [Line Items]
Shares outstanding (shares)	56,432,312	56,371,376
Common stock, voting rights, number of votes per share | vote	1
Common Stock | Common Class B
Share Capital [Line Items]
Shares outstanding (shares)	3,755	3,755
Common stock, voting rights, number of votes per share | vote	20