Annual report pursuant to Section 13 and 15(d)

Notes Payable (Details)

v3.8.0.1
Notes Payable (Details)
$ / shares in Units, $ in Thousands
 12 Months Ended
Oct. 15, 2013
USD ($)
Dec. 31, 2017
USD ($)
$ / shares
Dec. 31, 2016
$ / shares
Dec. 31, 2015
$ / shares
Jan. 31, 2015
item
Dec. 31, 2014
$ / shares
Dec. 31, 2013
Notes Payable              
Proceeds from Issuance of Long-term Debt $ 34,000            
Fixed interest rate (as a percent)             5.75%
Class Of Warrant Or Right, Exercise Price Of Warrants Or Rights | $ / shares   $ 0.97 $ 1.02 $ 1.71   $ 1.20  
Number of installments | item         28    
Sweetwater IDR Bond [Member]              
Notes Payable              
Maturity Date   Oct. 01, 2021          
Periodic payment amount   $ 19,891