Annual report pursuant to Section 13 and 15(d)

Summary of significant accounting policies (Details) - Impact to consolidated statements of operations due to adoption of ASU

v3.10.0.1
Summary of significant accounting policies (Details) - Impact to consolidated statements of operations due to adoption of ASU - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Jul. 31, 2018
Apr. 30, 2018
Jan. 31, 2018
Oct. 31, 2017
Jul. 31, 2017
Apr. 30, 2017
Jan. 31, 2017
Oct. 31, 2016
Jul. 31, 2018
Jul. 31, 2017
Jul. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Total Revenues                 $ 104,713 $ 107,804 $ 102,773
Provision for uncollectible accounts receivable                 3,690 2,775 2,336
Selling, general and administrative expenses                 44,465 44,092 43,741
Net loss $ (5,764) $ (3,016) $ (901) $ (640) $ 94 $ (71) $ (1,053) $ (1,474) (10,321) (2,504) $ 45,286
Accounting Standards Update 2014-09 [Member] | Reclassification Of Residual [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Provision for uncollectible accounts receivable                 10 (57)  
Selling, general and administrative expenses                 (10) 57  
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Total Revenues                 (3,700) (2,718)  
Provision for uncollectible accounts receivable                 (3,700) (2,718)  
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]                      
New Accounting Pronouncements or Change in Accounting Principle [Line Items]                      
Total Revenues                 101,013 105,086  
Selling, general and administrative expenses                 44,425 44,149  
Net loss                 $ (10,321) $ (2,504)