v3.19.2
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2019
Jul. 19, 2019
Cover page.    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2019  
Document Transition Report false  
Entity File Number 0-10235  
Entity Registrant Name GENTEX CORPORATION  
Entity Central Index Key 0000355811  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
Amendment Flag false  
Entity Incorporation, State or Country Code MI  
Entity Tax Identification Number 38-2030505  
Entity Address, Address Line One 600 N. Centennial  
Entity Address, City or Town Zeeland  
Entity Address, State or Province MI  
Entity Address, Postal Zip Code 49464  
City Area Code 616  
Local Phone Number 772-1800  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Title of 12(b) Security Common Stock, par value $0.06 per share  
Trading Symbol GNTX  
Security Exchange Name NASDAQ  
Entity Common Stock, Shares Outstanding   254,775,618