Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Narrative (Details)

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Commitments and Contingencies - Narrative (Details)
3 Months Ended 9 Months Ended 12 Months Ended
Jan. 31, 2019
USD ($)
Sep. 25, 2018
USD ($)
Mar. 22, 2018
USD ($)
ft²
Dec. 04, 2017
USD ($)
Jan. 09, 2017
USD ($)
May 02, 2016
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2018
USD ($)
Mar. 31, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
employee
Sep. 30, 2017
USD ($)
Dec. 31, 2015
USD ($)
Commitments and Contingencies [Line Items]                          
Payments to HPI over three-year period           $ 750,000              
Buy-out option payment to HPI           $ 1,000,000.0   $ 1,000,000.0     $ 1,000,000.0    
HPI out-licensing agreement term           3 years              
Sponsored laboratory study agreement expense               1,332,000   $ 1,061,000 $ 6,801,000 $ 2,260,000  
Employee agreements, special termination benefits, number of employees | employee                     8    
Employee agreements, termination benefits provided to key employees, aggregate amount                     $ 1,200,000    
MD Anderson                          
Commitments and Contingencies [Line Items]                          
License costs               110,000   100,000 200,000 200,000  
Houston Pharmaceuticals, Inc.                          
Commitments and Contingencies [Line Items]                          
License costs               100,000   100,000 1,200,000 200,000  
MD Anderson                          
Commitments and Contingencies [Line Items]                          
Payments for research and development agreement   $ 400,000   $ 350,000 $ 300,000       $ 240,000        
Sponsored laboratory study agreement expense               100,000   $ 40,000.00 300,000 $ 100,000  
Dermin                          
Commitments and Contingencies [Line Items]                          
Future payment to remove Germany                         $ 500,000
Lease Agreement For Corporate Office Space | IPX Memorial Drive Investors, LLC                          
Commitments and Contingencies [Line Items]                          
Leased office space (in square feet) | ft²     2,333                    
Term of operating lease (in months)     66 months                    
Operating lease, renewal term (in years)     5 years                    
Operating lease, monthly rent expense     $ 4,300                    
Operating lease, rent expense, annual increase in rent (as a percent)     3.00%                    
Maximum                          
Commitments and Contingencies [Line Items]                          
Payments for royalties                     600,000    
Maximum | MD Anderson                          
Commitments and Contingencies [Line Items]                          
License agreement, annual license fee                     100,000    
Maximum | MD Anderson | Commencement of Phase II and Phase III Clinical Trials                          
Commitments and Contingencies [Line Items]                          
Milestone payments liabilities               500,000     500,000    
Maximum | MD Anderson | Submission Of NDA And Receipt Of First Marketing Approval For Sale Of A Licensed Product                          
Commitments and Contingencies [Line Items]                          
Milestone payments liabilities               $ 600,000     $ 600,000    
Scenario, Forecast | MD Anderson                          
Commitments and Contingencies [Line Items]                          
Payments for research and development agreement $ 130,000           $ 270,000