Goodwill and Other Intangible Assets (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014		Sep. 27, 2013
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 307,365,845		$ 307,365,845		$ 307,365,845	[1]
Amortization expense, 2015	22,000,000		22,000,000
HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Goodwill							$ 307,400,000
Accumulated amortization	33,775,000		33,775,000		24,125,000
Amortization expense, 2016	22,000,000		22,000,000
Amortization expense, 2017	22,000,000		22,000,000
Amortization expense, 2018	22,000,000		22,000,000
Amortization expense, 2019	22,000,000		22,000,000
Gentex Patents
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Accumulated amortization	12,396,365		12,396,365		$ 11,065,153
Gentex Patents | HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	$ 5,500,000	$ 5,500,000	$ 11,000,000	$ 11,000,000
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.