Goodwill and Other Intangible Assets (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015		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, 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
Amortization expense, 2020	22,000,000		22,000,000
HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Goodwill							$ 307,400,000
Accumulated amortization	57,900,000		57,900,000		43,425,000
Gentex Patents
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Accumulated amortization	15,791,045		15,791,045		13,890,202
Patents and Other Intangible Assets
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Accumulated amortization	73,691,045		73,691,045		$ 57,315,202
Patents and Other Intangible Assets | HomeLink®
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	$ 5,600,000	$ 5,500,000	$ 16,700,000	$ 16,500,000

[1] Note: The condensed consolidated balance sheet at December 31, 2015 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.