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Note 1 - Business and Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2017
Notes Tables  
Schedule Of Estimated Useful Lives [Table Text Block]
Buildings (in years)
  
 
25
 
  
Leasehold improvements (in years)
  
 15
-
20
  
Machinery and equipment
— manufacturing and drilling (in years)
  
 
10
 
  
Machinery and equipment
— computers (in years)
  
 3
-
5
  
Office equipment
— furniture and fixtures (in years)
  
 5
-
15
  
Office equipment
— other (in years)
  
 5
-
10
  
Automobiles (in years)
  
 5
-
7
  
Schedule of Weighted Average Number of Shares [Table Text Block]
   
Year Ended December 31,
  
   
2017
   
2016
   
2015
 
   
(In thousands)
  
Weighted average number of shares used in computation of basic earnings per share
    
50,110
      
49,469
      
48,562
  
Add:
                        
Additional shares from the assumed exercise of employee stock options
    
659
      
671
      
625
  
                         
Weighted average number of shares used in computation of diluted earnings per share
    
50,769
      
50,140
      
49,187