Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Narrative (Details)

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Fair Value Measurements - Narrative (Details) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2018
Mar. 31, 2017
Mar. 31, 2016
Sep. 28, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                        
Secured debenture issuance costs and discount $ 1,827,000       $ 6,315,000       $ 1,827,000 $ 6,315,000    
Convertible notes, net of debt issuance costs and discounts of $1,827 and $6,315, respectively $ 3,873,000       $ 9,685,000       $ 3,873,000 $ 9,685,000    
Stock price (in dollars per share) $ 2.01       $ 0.94       $ 2.01 $ 0.94   $ 0.99
Change in fair value of convertible note embedded derivative liability                 $ (7,559,000) $ 475,000 $ 0  
Fair Value Adjustment of Warrants $ 682,000 $ 898,000 $ 1,164,000 $ 464,000 $ 650,000 $ (937,000) $ 140,000 $ 0 3,208,000 (147,000) $ 0  
Convertible Notes Payable                        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]                        
Original discount                       $ 4,916,000
Debt face amount 5,700,000       $ 16,000,000       5,700,000 $ 16,000,000   $ 16,000,000
Interest rate                       8.75%
Issuance of common stock related to debt                 10,300,000      
Secured debenture issuance costs and discount 1,827,000               1,827,000      
Convertible notes, net of debt issuance costs and discounts of $1,827 and $6,315, respectively $ 3,873,000               $ 3,873,000