Debt Securities (Tables)
 9 Months Ended
Apr. 30, 2019
Debt Securities [Abstract]  
Summary of marketable debt securities
  Amortized Cost  Gross Unrealized Gains  Gross Unrealized Losses  Fair Value 
  (in thousands) 
Available-for-sale securities:            
April 30, 2019:            
Municipal bonds $ 301  $         —  $        —  $301 
                 
July 31, 2018:                
Certificates of deposit* $3,032  $—  $—  $3,032 
U.S. Treasury notes  1,693   —   (1)  1,692 
Municipal bonds  888   —   —   888 
Total $5,613  $—  $(1) $5,612 

 

*Each of the Company’s certificates of deposit had a CUSIP, was purchased in the secondary market through a broker, and may be sold in the secondary market.
Summary of available-for-sale debt securities
  

Fair Value

 
 
  (in thousands) 
Within one year $301 
After one year through five years  — 
After five years through ten years  — 
After ten years  — 
Total $301 
Summary of available-for-sale securities, unrealized loss position
  Unrealized Losses  Fair Value 
  (in thousands) 
April 30, 2019:      
Total $—  $— 
         
July 31, 2018:        
U.S. Treasury notes $1  $1,692