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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
12 Months Ended
Feb. 28, 2017
May 31, 2016
Dec. 31, 2013
May 31, 2017
May 31, 2016
May 31, 2015
May 31, 2014
Significant Accounting Policies [Line Items]              
Cash and cash equivalents   $ 55,257,000   $ 77,567,000 $ 55,257,000 $ 66,061,000 $ 40,675,000
Cash held at foreign subsidiaries   5,320,000   8,132,000 5,320,000    
Short-term domestic certificates of deposit       25,355,000      
Commercial Paper       40,713,000      
Marketable securities   52,539,000   66,068,000 52,539,000    
Valuation allowance for inventory   1,550,000   2,000,000 1,550,000    
Depreciation expense       $ 8,783,000 $ 7,452,000 $ 6,318,000  
Weighted-average fair value per share of stock options granted       $ 15.86 $ 13.11 $ 11.91  
Percentage of customer credits for sales returns, pricing and other disputes, and other related matters against net revenue       3.00% 3.00% 3.00%  
Shipping and handling costs       $ 10,185,000 $ 9,734,000 $ 8,648,000  
Unremitted earnings of foreign subsidiaries       35,281,000      
Advertising costs       $ 1,643,000 $ 1,463,000 $ 1,371,000  
Shares excluded from computations of diluted net income per share       0 0 0  
Deferred tax assets, Current   1,775,000     $ 1,775,000    
Total assets and total liabilities decreased due to early adoption of ASU 2015-17   $ 1,775,000          
Minimum              
Significant Accounting Policies [Line Items]              
Marketable securities, maturity period       91 days      
Finite lived intangible assets, useful life       5 years      
Maximum              
Significant Accounting Policies [Line Items]              
Marketable securities, maturity period       1 year      
Finite lived intangible assets, useful life       25 years      
Buildings And Improvements | Minimum              
Significant Accounting Policies [Line Items]              
Property, plant and equipment estimated useful life       7 years 7 years 7 years  
Buildings And Improvements | Maximum              
Significant Accounting Policies [Line Items]              
Property, plant and equipment estimated useful life       39 years 39 years 39 years  
Furniture, Machinery and Equipment | Minimum              
Significant Accounting Policies [Line Items]              
Property, plant and equipment estimated useful life       3 years 3 years 3 years  
Furniture, Machinery and Equipment | Maximum              
Significant Accounting Policies [Line Items]              
Property, plant and equipment estimated useful life       10 years 10 years 10 years  
Customer Relationships              
Significant Accounting Policies [Line Items]              
Finite lived intangible assets, useful life       11 years 12 years    
Other Intangible Assets              
Significant Accounting Policies [Line Items]              
Finite lived intangible assets, useful life       11 years 12 years    
Neogen Latin America              
Significant Accounting Policies [Line Items]              
Percentage of ownership in subsidiaries   90.00%   90.00% 90.00%    
Percentage of ownership in subsidiaries before capital contribution     60.00%        
Percentage of ownership in subsidiaries after capital contribution     90.00%        
Neogen Do Brazil              
Significant Accounting Policies [Line Items]              
Percentage of ownership in subsidiaries   90.00%   100.00% 90.00%    
Percentage of ownership in subsidiaries after capital contribution 100.00%            
Customer one              
Significant Accounting Policies [Line Items]              
Account receivable percentage from major customer       10.00% 10.00%