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Condensed Consolidated Balance Sheets (Parenthetical) - shares
Mar. 31, 2019
Dec. 31, 2018
Condensed Consolidated Balance Sheets    
Class B preferred units, issued 31,310,896 31,310,896
Class B preferred units, outstanding 31,310,896 31,310,896
Units, issued 18,252,065 16,486,239
Units, outstanding 18,252,065 16,486,239