| Senior Convertible Notes (Tables) | 12 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Dec. 31, 2017 | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Debt Disclosure [Abstract] | |||||||||||||||||||||||||||||||||||||||||||||||||||||
| Schedule of Debt, Accrued Interest and Interest Expense | Debt and accrued interest at December 31, 2017 and interest expense for the year ended December 31, 2017 are as follows: 
 
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- Definition Schedule of Debt, Accrued Interest and Interest Expense [Table Text Block] No definition available. 
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- References No definition available. 
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