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Stock-Based Compensation Plans - Narrative (Details) |  | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Jun. 30, 2022 shares | May 31, 2022 shares | Sep. 30, 2024 USD ($) plan shares | Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) plan shares | Sep. 30, 2023 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Compensation expense for share-based payments | $ |  |  | $ 9,590,588 | $ 10,948,031 | $ 31,042,268 | $ 29,212,236
Employee Stock |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares issued under the omnibus plan (in shares) |  |  |  |  | 1,624,122 |
Number of shares authorized (in shares) | 2,000,000 |  |  |  |  |
ESPP discount rate | 85.00% |  |  |  |  |
ESPP discount rate recognized as compensation expense | 15.00% |  |  |  |  |
Omnibus Incentive Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total grants in period (in shares) |  |  |  |  | 11,109,647 |
Shares issued under the omnibus plan (in shares) |  |  |  |  | 29,672,008 |
Number of shares authorized (in shares) |  |  | 45,000,000 |  | 45,000,000 |
Employee Stock Option Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  | $ 5,834,690 |  | $ 5,834,690 |
Employee Stock Option Plan | Minimum |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Option vesting period |  |  |  |  | 1 year |
Option expiration period |  |  |  |  | 5 years |
Employee Stock Option Plan | Maximum |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Option vesting period |  |  |  |  | 5 years |
Option expiration period |  |  |  |  | 10 years |
Restricted Stock Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Unrecognized compensation cost | $ |  |  | 52,836,541 |  | $ 52,836,541 |
Restricted period, maximum |  |  |  |  | 10 years |
Amortization expense | $ |  |  | $ 5,915,930 | 6,369,348 | $ 19,487,110 | 18,178,157
Gentex Corporation Employee Stock Purchase Plan | Employee Stock |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares issued under the omnibus plan (in shares) |  |  |  |  | 442,718 |
Number of shares authorized (in shares) |  | 2,000,000 |  |  |  |
ESPP discount rate |  | 85.00% |  |  |  |
ESPP discount rate recognized as compensation expense |  | 15.00% |  |  |  |
Equity Incentive Plans |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of plans | plan |  |  | 2 |  | 2 |
Performance Shares |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Compensation expense for share-based payments | $ |  |  | $ 1,573,201 | 2,463,158 | $ 5,369,466 | 4,600,386
Unrecognized compensation cost | $ |  |  | 15,768,739 |  | $ 15,768,739 |
Performance Shares | Omnibus Incentive Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares issued under the omnibus plan (in shares) |  |  |  |  | 4,127,603 |
Performance Share Awards |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Compensation expense for share-based payments | $ |  |  | $ 453,393 | $ 441,115 | $ 1,342,032 | $ 1,082,333
Option vesting period |  |  |  |  | 4 years |

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