v3.7.0.1
Document And Entity Information - shares
6 Months Ended
Jun. 30, 2017
Jul. 21, 2017
Document And Entity Information [Abstract]    
Entity Registrant Name GENTEX CORPORATION  
Entity Central Index Key 0000355811  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Jun. 30, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Trading Symbol gntx  
Entity Common Stock, Shares Outstanding   285,549,444