Annual report pursuant to Section 13 and 15(d)

Income taxes (Details)

v3.19.3
Income taxes (Details) - USD ($)
 5 Months Ended 7 Months Ended 12 Months Ended
Dec. 31, 2017
Jul. 31, 2018
Jul. 31, 2019
Jul. 31, 2018
Jul. 31, 2017
Income taxes (Details) [Line Items]          
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent 34.00% 21.00% (21.00%) 26.40% 34.00%
Tax Cut and Job Act 2017 Deferred Tax Assets Valuation Allowance     $ 0 $ 11,500,000  
Effective Income Tax Rate Reconciliation, Tax Credit, Amount     0 1,100,000  
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount     (900,000) 8,100,000  
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration     59,100,000    
Deferred Tax Assets Research and Development and Other Tax Credit Carryforwards   $ 1,286,000 1,350,000 $ 1,286,000  
Deferred Tax Assets, Operating Loss Carryforwards     2,700,000    
Foreign Loss Carryforwards     15,400,000    
Liability for Uncertain Tax Position     0    
U.S. Federal Tax [Member]          
Income taxes (Details) [Line Items]          
Deferred Tax Assets Research and Development and Other Tax Credit Carryforwards     $ 1,300,000    
Maximum [Member]          
Income taxes (Details) [Line Items]          
Operating Loss Carryforward Expiration Year End     2038    
Maximum [Member] | Domestic Tax Authority [Member]          
Income taxes (Details) [Line Items]          
Operating Loss Carryforwards Expiration Year     2030    
Maximum [Member] | Research Tax Credit Carryforward [Member]          
Income taxes (Details) [Line Items]          
Tax Credit Carryforward Expiration Year     2039    
Minimum [Member]          
Income taxes (Details) [Line Items]          
Operating Loss Carryforward Expiration Year Begining     2037    
Minimum [Member] | Domestic Tax Authority [Member]          
Income taxes (Details) [Line Items]          
Operating Loss Carryforwards Expiration Year     2038    
Minimum [Member] | Research Tax Credit Carryforward [Member]          
Income taxes (Details) [Line Items]          
Tax Credit Carryforward Expiration Year     2025