Goodwill and Other Intangible Assets (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014		Dec. 31, 2013	Sep. 27, 2013
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 307,365,845		$ 307,365,845	[1]
Amortization expense, 2015	22,000,000
HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Goodwill					307,400,000	337,600,000
Goodwill that is expected to be deductible for tax purposes			307,400,000
Accumulated amortization	28,950,000		24,125,000
Amortization expense, 2016	22,000,000
Amortization expense, 2017	22,000,000
Amortization expense, 2018	22,000,000
Amortization expense, 2019	22,000,000
Gentex Patents
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Accumulated amortization	11,713,249		11,065,153
Gentex Patents | HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	5,500,000
Intangible Assets [Member] | HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Amortization expense		$ 5,500,000

[1] Note: The condensed consolidated balance sheet at December 31, 2014 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.