Income taxes (Details) - USD ($) $ in Thousands	3 Months Ended		5 Months Ended	6 Months Ended		7 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Dec. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jul. 31, 2018
Income taxes (Details) [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			35.00%
Effective Income Tax Rate Reconciliation, Percent	54.90%			41.60%
Income Tax Expense (Benefit) (in Dollars)	$ (1,097)	$ 0		$ (1,097)	$ 0
Alternate Minimum Tax [Member]
Income taxes (Details) [Line Items]
Effective Income Tax Rate Reconciliation, Tax Credit, Amount (in Dollars)	$ 1,100
Scenario, Plan [Member]
Income taxes (Details) [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent						21.00%