Loss Per Share - Calculation of Basic and Diluted Loss Per Share (Details) - USD ($)
 3 Months Ended 12 Months Ended
Aug. 15, 2019
May 15, 2019
Oct. 31, 2020
Jul. 31, 2020
Apr. 30, 2020
Jan. 31, 2020
Oct. 31, 2019
Jul. 31, 2019
Apr. 30, 2019
Jan. 31, 2019
Oct. 31, 2020
Oct. 31, 2019
Oct. 31, 2018
Numerator                          
Net loss     $ (18,856,000) $ (15,331,000) $ (14,769,000) $ (40,151,000) $ (35,179,000) $ (5,311,000) $ (19,530,000) $ (17,548,000) $ (89,107,000) $ (77,568,000) $ (47,334,000)
Warrant exchange                     (37,086,000) 0 0
Preferred dividends — Series B                         (3,200,000)
Net loss attributable to common stockholders     (19,656,000) (16,131,000) (15,569,000) (41,082,000) (36,003,000) (8,328,000) (22,876,000) (33,038,000) $ (92,438,000) $ (100,245,000) $ (62,168,000)
Denominator                          
Weighted average common shares outstanding - basic                     221,960,288 55,081,266 6,896,189
Effect of dilutive securities [1]                     0 0 0
Weighted average common shares outstanding - diluted                     221,960,288 55,081,266 6,896,189
Net loss to common stockholders per share - basic                     $ (0.42) $ (1.82) $ (9.01)
Net loss to common stockholders per share - diluted [1]                     $ (0.42) $ (1.82) $ (9.01)
Series A Warrant [Member]                          
Numerator                          
Warrant exchange                 (3,169,000)   $ 0 $ (3,169,000) $ 0
Series C Preferred Stock [Member]                          
Numerator                          
Preferred stock deemed dividends and redemption value adjustments, net                     0 (6,522,000) (9,559,000)
Series B Preferred Stock [Member]                          
Numerator                          
Preferred dividends — Series B $ 0 $ 0 $ (800,000) $ (800,000) $ (800,000) $ (931,000) $ (821,000) $ (810,000) $ (800,000) $ (800,000) (3,331,000) (3,231,000) (3,200,000)
Series D Preferred Stock [Member]                          
Numerator                          
Preferred stock deemed dividends and redemption accretion                     $ 0 $ (9,755,000) $ (2,075,000)
[1] Due to the net loss to common stockholders in each of the years presented above, diluted earnings per share was computed without consideration to potentially dilutive instruments as their inclusion would have been antidilutive.