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Goodwill and Other Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2017 | Dec. 31, 2016
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Intangible assets, net | $ 298,625,000 | $ 308,275,000 | [1]
Gentex Patents |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible assets, gross | 33,939,953 | 33,002,468 |
Finite-lived intangible assets, accumulated amortization | (17,473,999) | (16,481,728) |
Finite-lived intangible assets, net | 16,465,954 | 16,520,740 |
Patents and Other Intangible Assets |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible assets, accumulated amortization | (89,848,999) | (79,206,728) |
Intangible assets, gross | 404,939,953 | 404,002,468 |
Intangible assets, net | 315,090,954 | 324,795,740 |
HomeLink® |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible assets, accumulated amortization | (72,375,000) | (62,725,000) |
Intangible assets, gross | 371,000,000 | 371,000,000 |
Intangible assets, net | 298,625,000 | 308,275,000 |
HomeLink® | Homelink Technology |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible assets, gross | 180,000,000 | 180,000,000 |
Finite-lived intangible assets, accumulated amortization | (56,250,000) | (48,750,000) |
Finite-lived intangible assets, net | $ 123,750,000 | $ 131,250,000 |
HomeLink® | Homelink Technology | Minimum [Member] |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible asset, useful life | 12 years | 12 years |
HomeLink® | Existing Customer Platforms |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible assets, gross | $ 43,000,000 | $ 43,000,000 |
Finite-lived intangible assets, accumulated amortization | (16,125,000) | (13,975,000) |
Finite-lived intangible assets, net | $ 26,875,000 | $ 29,025,000 |
Finite-lived intangible asset, useful life | 10 years | 10 years |
HomeLink® | HomeLink Trade Names and Trademarks |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Indefinite-lived intangible assets | $ 52,000,000 | $ 52,000,000 |
HomeLink® | Exclusive Licensing Agreement |  |  |
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items] |  |  |
Indefinite-lived intangible assets | $ 96,000,000 | $ 96,000,000 |
[1] | Note: The condensed consolidated balance sheet at December 31, 2016 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.

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