Gentex (GNTX) 10-Q 5 May 15 2015 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 22, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	GENTEX CORPORATION
Entity Central Index Key	355811
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Trading Symbol	gntx
Entity Common Stock, Shares Outstanding		294,192,247

Unaudited_Condensed_Consolidat

Unaudited Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
CURRENT ASSETS
Cash and cash equivalents	$549,911,648	$497,429,804	[1]
Accounts receivable, net	201,782,059	168,008,704	[1]
Inventories	145,563,949	141,757,884	[1]
Prepaid expenses and other	33,509,205	49,441,302	[1]
Total current assets	930,766,861	856,637,694	[1]
PLANT AND EQUIPMENT—NET	372,616,211	373,390,992	[1]
OTHER ASSETS
Goodwill	307,365,845	307,365,845	[1]
Long-term investments	115,497,100	114,642,567	[1]
Intangible Assets, net	342,050,000	346,875,000	[1]
Patents and other assets, net	23,139,088	23,627,931	[1]
Total other assets	788,052,033	792,511,343	[1]
Total assets	2,091,435,105	2,022,540,029	[1]
CURRENT LIABILITIES
Accounts payable	73,284,660	71,456,983	[1]
Accrued liabilities	90,417,747	61,974,180	[1]
Total current liabilities	163,702,407	133,431,163	[1]
LONG TERM DEBT	256,250,000	258,125,000	[1]
DEFERRED INCOME TAXES	58,000,242	59,571,421	[1]
TOTAL LIABILITIES	477,952,649	451,127,584	[1]
SHAREHOLDERS’ INVESTMENT
Common stock	17,680,567	17,714,877	[1]
Additional paid-in capital	567,470,322	553,836,483	[1]
Retained earnings	1,019,527,620	988,548,070	[1]
Accumulated other comprehensive income	8,803,947	11,313,015	[1]
Total shareholders’ investment	1,613,482,456	1,571,412,445	[1]
Total liabilities and shareholders’ investment	$2,091,435,105	$2,022,540,029	[1]
[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.

Unaudited_Condensed_Consolidat1

Unaudited Condensed Consolidated Statements of Income (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
NET SALES	$368,937,455	$335,739,344
COST OF GOODS SOLD	225,845,046	204,440,537
Gross profit	143,092,409	131,298,807
OPERATING EXPENSES:
Engineering, research and development	21,587,551	20,489,227
Selling, general & administrative	13,796,352	13,632,034
Total operating expenses	35,383,903	34,121,261
Income from operations	107,708,506	97,177,546
OTHER INCOME
Investment income	612,025	325,158
Other, net	97,359	4,189,386
Total other income	709,384	4,514,544
Income before provision for income taxes	108,417,890	101,692,090
PROVISION FOR INCOME TAXES	31,234,449	33,126,019
NET INCOME	$77,183,441	$68,566,071
EARNINGS PER SHARE:
Basic (in dollars per share)	$0.26	$0.24
Diluted (in dollars per share)	$0.26	$0.23
Cash Dividends Declared per Share (in dollars per share)	$0.08	$0.07

Unaudited_Condensed_Consolidat2

Unaudited Condensed Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$77,183,441	$68,566,071
Other comprehensive income (loss) before tax:
Foreign currency translation adjustments	-942,974	-91,250
Unrealized gains (losses) on derivatives	-1,831,690	0
Unrealized gains (losses) on available-for sales securities, net	-577,685	-3,692,791
Other comprehensive income (loss), before tax	-3,352,349	-3,784,041
Provision (Benefit) for income taxes related to components of other comprehensive income	-843,281	-1,292,477
Other comprehensive income (loss), net of tax	-2,509,068	-2,491,564
Comprehensive Income	$74,674,373	$66,074,507

Unaudited_Condensed_Consolidat3

Unaudited Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$77,183,441		$68,566,071
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	21,279,105		19,825,402
Gain on disposal of assets	-44,414		-54,520
Loss on disposal of assets	221,953		218,409
Gain on sale of investments	-2,912,864		-5,049,229
Loss on sale of investments	300,593		25,808
Deferred income taxes	-15,354		-1,614,318
Stock-based compensation expense related to employee stock options, employee stock purchases and restricted stock	5,813,951		4,742,080
Excess tax benefits from stock-based compensation	-1,073,744		-702,580
Change in operating assets and liabilities:
Accounts receivable, net	-33,773,355		-28,290,721
Inventories	-3,806,065		-8,275,303
Prepaid expenses and other	15,219,554		534,133
Accounts payable	1,827,677		7,889,358
Accrued liabilities, excluding dividends declared	27,731,368		39,907,356
Net cash provided by operating activities	107,951,846		97,721,946
Activity in available-for-sale securities:
Sales proceeds	7,540,449		23,856,516
Purchases	-6,360,397		-24,487,944
Plant and equipment additions	-15,160,355		-16,417,890
Proceeds from sale of plant and equipment	4		35,005
(Increase) in other assets	-1,150,642		-285,354
Net cash (used for) investing activities	-15,130,941		-17,299,667
CASH FLOWS (USED FOR) PROVIDED BY FINANCING ACTIVITIES:
Repayment of long-term debt	-1,875,000		-1,875,000
Issuance of common stock from stock plan transactions	9,131,177		6,227,631
Cash dividends paid	-23,619,837		-20,380,923
Repurchases of common stock	-25,049,145		0
Excess tax benefits from stock-based compensation	1,073,744		702,580
Net cash (used for) financing activities	-40,339,061		-15,325,712
NET INCREASE IN CASH AND CASH EQUIVALENTS	52,481,844		65,096,567
CASH AND CASH EQUIVALENTS, beginning of period	497,429,804	[1]	309,591,724
CASH AND CASH EQUIVALENTS, end of period	$549,911,648		$374,688,291
[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.

Basis_of_Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation
	The unaudited condensed consolidated financial statements included herein have been prepared by the Company, pursuant to the rules and regulations of the Securities and Exchange Commission. Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States have been condensed or omitted pursuant to such rules and regulations, although the Company believes that the disclosures are adequate to make the information presented not misleading. It is suggested that these unaudited condensed consolidated financial statements be read in conjunction with the financial statements and notes thereto included in the Company's 2014 annual report on Form 10-K. In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments, consisting of only a normal and recurring nature, necessary to present fairly the financial position of the Company as of March 31, 2015, and the results of operations and cash flows for the interim periods presented.

Adoption_of_New_Accounting_Sta

Adoption of New Accounting Standards	3 Months Ended
	Mar. 31, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Adoption of New Accounting Standards	Adoption of New Accounting Standards
	In May 2014 the Financial Accounting Standards Board (FASB) issued the Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606), that will supersede nearly all existing revenue recognition guidance under US GAAP. The core principle of the guidance is that an entity should recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard will be effective for public entities for annual and interim periods beginning after December 15, 2016.
	Entities can choose to apply the standard using either the full retrospective approach or a modified retrospective approach. Entities electing the full retrospective adoption will apply the standard to each period presented in the financial statements. This means that entities will have to apply the new guidance as if it had been in effect since the inception of all its contracts with customers presented in the financial statements. Entities that elect the modified retrospective approach will apply the guidance retrospectively only to the most current period presented in the financial statements. This means that entities will have to recognize the cumulative effect of initially applying the new standard as an adjustment to the opening balance of retained earnings at the date of initial application. The new revenue standard will be applied to contracts that are in progress at the date of initial application.
	The Company is currently evaluating which adoption method it plans to use and is assessing the potential effect the new standard will have on its consolidated financial statements.

Goodwill_and_Other_Intangible_

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets
	Goodwill represents the cost of an acquisition in excess of the fair values assigned to identifiable net assets acquired. On September 27, 2013, the Company recorded Goodwill of $337.6 million as part of the HomeLink® acquisition. As of December 31, 2013, the Company adjusted recorded Goodwill to $307.4 million resulting from refinement of the purchase accounting estimates, based on updated valuations of tangible and intangible assets acquired as part of the HomeLink® acquisition, which the Company finalized the purchase accounting estimates in the first quarter of 2014. The amount of Goodwill that is expected to be deductible for tax purposes is $307.4 million. The carrying value of Goodwill as of December 31, 2014 and March 31, 2015 was $307.4 million.
	In addition to annual impairment testing, which was performed in the fourth quarter of 2014 and indicated that the estimated fair value of the Automotive reporting unit exceeded its corresponding carrying amount including goodwill, the Company continuously monitors for events and circumstances that could negatively impact the key assumptions in determining fair value thus resulting in the need for interim impairment testing, including long-term revenue growth projections, profitability, discount rates, recent market valuations from transactions by comparable companies, volatility in the Company's market capitalization, and general industry, market and macro-economic conditions. No such events or circumstances in the most recently completed quarter indicated the need for interim impairment testing.
	The patents and intangible assets and related change in carrying values are set forth in the table belows:
	As of March 31, 2015:
	Other Intangible Assets	Gross		Accumulated Amortization			Net		Assumed Useful Life
	Gentex Patents	$	30,363,189	$	(11,713,249	)	$	18,649,940	various
	Other Intangible Assets
	HomeLink®Trade Names and Trademarks	$	52,000,000	$	—		$	52,000,000	Indefinite
	HomeLink® Technology	180,000,000		(22,500,000		)	157,500,000		12 years
	Existing Customer Platforms	43,000,000		(6,450,000		)	36,550,000		10 years
	Exclusive Licensing Agreement	96,000,000		—			96,000,000		Indefinite
	Total Other Intangible Assets	$	371,000,000	$	(28,950,000	)	$	342,050,000
	Total Patents & Other Intangible Assets	$	401,363,189	$	(40,663,249	)	$	360,699,940
	As of December 31, 2014:
	Other Intangible Assets	Gross		Accumulated Amortization			Net		Assumed Useful Life
	Gentex Patents	$	30,132,116	$	(11,065,153	)	$	19,066,963	various
	HomeLink®Trade Names and Trademarks	$	52,000,000	$	—		$	52,000,000	Indefinite
	HomeLink® Technology	180,000,000		(18,750,000		)	$	161,250,000	12 years
	Existing Customer Platforms	43,000,000		(5,375,000		)	$	37,625,000	10 years
	Exclusive Licensing Agreement	96,000,000		—			$	96,000,000	Indefinite
	Total other identifiable intangible assets	$	371,000,000	$	(24,125,000	)	$	346,875,000
	Total Patents & Other Intangible Assets	$	401,132,116	$	(35,190,153	)	$	365,941,963
	Amortization expense on patents and intangible assets was $5.5 million during the three month periods ended March 31, 2015 and March 31, 2014, respectively.
	Excluding the impact of any future acquisitions, the Company continues to estimate amortization expense for each of the years ended December 31, 2015, 2016, 2017, 2018 and 2019 to be approximately $22 million annually.

Investments

Investments	3 Months Ended
	Mar. 31, 2015
Investments [Abstract]
Investments	Investments
	The Company follows the provisions of ASC 820, “Fair Value Measurements and Disclosures” for its financial assets and liabilities, and to its non-financial assets and liabilities subject to fair value measurements. ASC 820 provides a framework for measuring the fair value of assets and liabilities. This framework is intended to provide increased consistency in how fair value determinations are made under various existing accounting standards that permit, or in some cases, require estimates of fair-market value. This standard also expanded financial statement disclosure requirements about a company’s use of fair-value measurements, including the effect of such measure on earnings. The cost of securities sold is based on the specific identification method.
	The Company’s investment securities (common stocks and mutual funds) are classified as available for sale and are stated at fair value based on quoted market prices, and as such are classified as Level 1 assets.
	Assets or liabilities that have recurring fair value measurements are shown below as of March 31, 2015, and December 31, 2014:
	As of March 31, 2015:
				Fair Value Measurements at Reporting Date Using
		Total as of		Quoted Prices in		Significant			Significant
				Active Markets for		Other			Unobservable
				Identical Assets		Observable			Inputs
						Inputs
	Description	31-Mar-15		(Level 1)		(Level 2)			(Level 3)
	Cash & Cash Equivalents	$	549,911,648	$	549,911,648	$	—		$	—
	Short-Term Investments:
	Other	560		560		—			—
	Long-Term Investments:
	Common Stocks	24,161,865		24,161,865		—			—
	Mutual Funds – Equity	91,335,235		91,335,235		—			—
	Total	$	665,409,308	$	665,409,308	$	—		$	—
	As of December 31, 2014:
				Fair Value Measurements at Reporting Date Using
		Total as of		Quoted Prices in		Significant Other			Significant
				Active Markets for		Observable			Unobservable
				Identical Assets		Inputs			Inputs
	Description	31-Dec-14		(Level 1)		(Level 2)			(Level 3)
	Cash & Cash Equivalents	$	497,429,804	$	497,429,804	$	—		$	—
	Short-Term Investments:
	Other	1,021		1,021		—			—
	Long-Term Investments:
	Common Stocks	24,648,451		24,648,451		—			—
	Mutual Funds – Equity	89,994,116		89,994,116		—			—
	Total	$	612,073,392	$	612,073,392	$	—		$	—
	The amortized cost, unrealized gains and losses, and market value of investment securities are shown as of March 31, 2015, and December 31, 2014:
	As of March 31, 2015:
				Unrealized
		Cost		Gains		Losses			Market Value
	Short-Term Investments:
	Other	$	560	$	—	$	—		$	560
	Long-Term Investments:
	Common Stocks	18,804,767		5,825,050		(467,952		)	24,161,865
	Mutual Funds – Equity	80,549,522		11,109,462		(323,749		)	91,335,235
	Total	$	99,354,849	$	16,934,512	$	(791,701	)	$	115,497,660
	As of December 31, 2014:
				Unrealized
		Cost		Gains		Losses			Market Value
	Short-Term Investments:
	Other	1,021		—		—			1,021
	Long-Term Investments:
	Common Stocks	$	17,069,742	$	7,933,717	$	(355,008	)	$	24,648,451
	Mutual Funds – Equity	80,852,329		9,922,204		(780,417		)	89,994,116
	Total	$	97,923,092	$	17,855,921	$	(1,135,425	)	$	114,643,588
	Unrealized losses on investments as of March 31, 2015, are as follows:
		Aggregate Unrealized Losses		Aggregate Fair Value
	Less than one year	$	791,701	$	15,894,733
	Unrealized losses on investments as of December 31, 2014, are as follows:
		Aggregate Unrealized Losses		Aggregate Fair Value
	Less than one year	$	1,135,425	$	19,972,258
	ASC 320, “Accounting for Certain Investments in Debt and Equity Securities”, as amended, provides guidance on determining when an investment is other than temporarily impaired. The Company reviews its equity investment portfolio for any unrealized losses that would be deemed other-than-temporary and require the recognition of an impairment loss in income. If the cost of an investment exceeds its fair value, the Company evaluates, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and the Company’s intent and ability to hold the investments. Management also considers the type of security, related-industry and sector performance, as well as published investment ratings and analyst reports, to evaluate its portfolio. Once a decline in fair value is determined to be other than temporary, an impairment charge is recorded and a new cost basis in the investment is established. If market, industry, and/or investee conditions deteriorate, the Company may incur future impairments. No equity investment losses were considered to be other than temporary at March 31, 2015.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Inventories	Inventories consisted of the following at the respective balance sheet dates:
		March 31, 2015		December 31, 2014
	Raw materials	$	91,275,645	$	90,780,320
	Work-in-process	24,207,804		24,135,944
	Finished goods	30,080,500		26,841,620
	Total Inventory	$	145,563,949	$	141,757,884

Earnings_Per_Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share
	The following table reconciles the numerators and denominators used in the calculation of basic and diluted earnings per share (EPS), adjusted for the 2 for 1 stock split effected in the form of a 100% stock dividend issued on December 31, 2014:
		Three Months Ended March 31,
		2015		2014
	Numerators:
	Numerator for both basic and diluted EPS, net income	$	77,183,441	$	68,566,071
	Denominators:
	Denominator for basic EPS, weighted-average shares outstanding	295,031,431		289,836,812
	Potentially dilutive shares resulting from stock plans	3,562,712		3,600,202
	Denominator for diluted EPS	298,594,143		293,437,014
	Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive	1,184,635		1,188,830

StockBased_Compensation_Plans

Stock-Based Compensation Plans	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans
	As of March 31, 2015, the Company had four equity incentive plans which include two stock option plans, a restricted stock plan and an employee stock purchase plan All plans and any prior material amendments thereto have previously been approved by shareholders (with an amendment to the restricted stock plan and an amendment to the employee stock purchase plan also up for vote by shareholders at the Company's 2015 Annual Meeting of Shareholders). Readers should refer to Note 5 of our consolidated financial statements in our Annual Report on Form 10-K for the calendar year ended December 31, 2014, for additional information related to these stock-based compensation plans.
	The Company recognized compensation expense for share-based payments of $4,846,051 for the first quarter ended March 31, 2015. Compensation cost capitalized as part of inventory as of March 31, 2015, was $239,947.
	Employee Stock Option Plan
	In May 2014, the Employee Stock Option Plan was approved by shareholders, amending and restating a prior plan. The Company may grant up to 24,000,000 shares of common stock under the plan. The purpose of the plan is to provide an opportunity to use stock options as a means of recruiting new managerial and technical personnel and as a means for retaining certain employees of the Company and allow them to purchase shares of common stock of the Corporation and thereby have an additional incentive to contribute to the prosperity of the Company.
	The fair value of each option grant in the employee stock option plan was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions for the indicated periods:
		Three Months Ended March 31,
		2015		2014
	Dividend Yield (1)	2.14	%	2.33	%
	Expected volatility (2)	36.8	%	40.36	%
	Risk-free interest rate (3)	1.37	%	1.74	%
	Expected term of options (years) (4)	4.29		3.95
	Weighted-avg. grant date fair value	$4.76		$4.27
	(1)Represents the Company’s estimated cash dividend yield over the expected term of option grant.
	(2)	Amount is determined based on analysis of historical price volatility of the Company’s common stock. The expected volatility is based on the daily percentage change in the price of the stock over a period equal to the expected term of the option grant.
	(3)	Represents the U.S. Treasury yield over the expected term of the option grant.
	(4)	Represents the period of time that options granted are expected to be outstanding. Based on analysis of historical option exercise activity, the Company has determined that all employee groups exhibit similar exercise and post-vesting termination behavior.
	Under the plan, the option exercise price equals the stock’s market price on date of grant. The options vest after one to five years, and expire after five to seven years. As of March 31, 2015, there was $25,868,764 of unrecognized compensation cost related to share-based payments which is expected to be recognized over the vesting periods.
	Non-employee Director Stock Option Plan
	As of March 31, 2015, there was $0 of unrecognized compensation cost under the plan related to share-based payments. The Company has granted options on 266,000 shares under the director plan through March 31, 2015. Under the plan, the option exercise price equals the stock’s market price on the date of grant. The options vest after six months, and expire after ten years.
	Employee Stock Purchase Plan
	The Company has an employee stock purchase plan covering 2,000,000 shares of common stock. Under the plan, the Company sells shares at 85% of the stock’s market price at date of purchase. Under ASC 718, the 15% discounted value is recognized as compensation expense.
	Restricted Stock Plan
	The Company has a restricted stock plan covering 4,000,000 shares of common stock. The purpose of the plan is to permit grants of shares, subject to restrictions, to key employees of the Company as a means of retaining and rewarding them for long-term performance and to increase their ownership in the Company. Shares awarded under the plan entitle the shareholder to all rights of common stock ownership except that the shares may not be sold, transferred, pledged, exchanged or otherwise disposed of during the restriction period. The restriction period is determined by the Compensation Committee, appointed by the Board of Directors, but may not exceed ten years under the terms of the plan. As of March 31, 2015, the Company had unearned stock-based compensation of $11,753,501 associated with these restricted stock grants. The unearned stock-based compensation related to these grants is being amortized to compensation expense over the applicable restriction periods. Amortization expense from restricted stock grants in the three months ended March 31, 2015 was $967,900.

Comprehensive_Income

Comprehensive Income	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Comprehensive Income	Comprehensive Income
	Comprehensive income reflects the change in equity of a business enterprise during a period from
	transactions and other events and circumstances from non-owner sources. For the Company,
	comprehensive income represents net income adjusted for unrealized gains and losses on certain
	investments and foreign currency translation adjustments.
	The following table presents the net changes in the Company's accumulated other comprehensive income by component: (All amounts shown are net of tax).
		Three Months Ended March 31,
		2015				2014
	Foreign currency translation adjustments:
	Balance at beginning of period	$	1,403,899			$	2,507,922
	Other Comprehensive (loss) income before reclassifications	(942,974		)		(91,250		)
	Amounts reclassified from accumulated other comprehensive income	—				—
	Net current-period change	(942,974		)		(91,250		)
	Balance at end of period	460,925				2,416,672
	Unrealized gains on available-for-sale securities:
	Balance at beginning of period	10,868,322				19,467,441
	Other Comprehensive income (loss) before reclassifications	(2,073,471		)		864,910
	Amounts reclassified from accumulated other comprehensive income	1,697,976				(3,265,224		)
	Net current-period change	(375,495		)		(2,400,314		)
	Balance at end of period	10,492,827				17,067,127
	Unrealized gains (losses) on derivatives:
	Balance at beginning of period	(959,206		)		—
	Other comprehensive income (loss) before reclassifications	—				—
	Amounts reclassified from accumulated other comprehensive income	(1,190,599		)		—
	Net current-period change	(1,190,599		)		—
	Balance at end of period	(2,149,805		)		—
	Accumulated other comprehensive income, end of period	$	8,803,947			$	19,483,799
	The following table presents details of reclassifications out of other comprehensive income for the three months ended March 31, 2015 and 2014.
	Details about Accumulated Other Comprehensive Income Components		Amounts Reclassified from Other Comprehensive Income							Affected Line item in the Statement of Consolidated Income
			Three Months Ended March 31,
			2015				2014
	Unrealized gains on available-for-sale securities
	Realized gain on sale of securities		$	2,612,271			$	5,023,421		Other, net
	Provision for Income Taxes		(914,295		)		(1,758,197		)	Provision for Income Taxes
	Total reclassifications for the period		$	1,697,976			$	3,265,224		Net of tax

Debt_and_Financing_Arrangement

Debt and Financing Arrangements	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt and Financing Arrangements	Debt and Financing Arrangements
	On September 27, 2013, the Company entered into a Credit Agreement (the “Credit Agreement”) with certain banks and agents.
	Pursuant to the Credit Agreement, the Company is borrower under a $150 million senior revolving credit facility (“Revolver”) and a $150 million term loan facility (“Term Loan”). Under the terms of the Credit Agreement, the Company is entitled, to further request an additional aggregate principal amount of up to $75 million, subject to the satisfaction of certain conditions. In addition, the Company is entitled to the benefit of swing loans from amounts otherwise available under the Revolver in the aggregate principal amount of up to $20 million and to request Letters of Credit from amounts otherwise available under the Revolver in the aggregate principle amount up to $20 million, both subject to certain conditions. The obligations of the Company under the Credit Agreement are not secured, but are subject to certain covenants. The Revolver expires and the Term Loan matures on September 27, 2018.
	During the three months ended March 31, 2015, the Company made principal repayments of $1.9 million, plus accrued interest, on the Term Loan, and accrued interest on the Revolver. The Company used cash and cash equivalents to fund the payments. As of March 31, 2015, $125 million was outstanding on the Revolver with availability of an additional $25 million. Under current terms of the Term Loan, the Company will make principal repayments of $7.5 million annually through the maturity date of the Term Loan. As of March 31, 2015, $138.8 million was outstanding under the Term Loan.
	As of March 31, 2015, the borrowing rate on both its Term Loan and Revolver are derived from the one month LIBOR, and based on the Company's leverage ratio as of March 31, 2015, the interest rate on its borrowings is equal to 1.18%. Interest expense are netted within the "Other, net" section of the Consolidated Statements of Income and were $0.8 million and $0.9 million during the three months ended March 31, 2015 and March 31, 2014, respectively.
	The Credit Agreement contains customary representations and warranties and certain covenants that place certain limitations on the Company.
	As of March 31, 2015, the Company was in compliance with its covenants under the Credit Agreement.
	Interest Rate Swap
	On October 1, 2014 the Company entered into an interest rate swap transaction with a bank (the “Counterparty”). The Counterparty is among the syndicate of lenders under the existing Credit Agreement entered into on September 27, 2013. The Company entered into the interest rate swap transaction to mitigate the Company’s floating rate interest risk on an aggregate of $150 million of the Company’s debt that is currently outstanding under the Credit Agreement. The interest rate swap has an effective date of July 31, 2015 and a termination date of September 27, 2018 (which is the expiration date of the Credit Agreement). The Company is required to make certain monthly fixed rate payments to the Counterparty calculated on a notional amount of $150 million for the rate swap, while the Counterparty is obligated to make monthly floating rate payments to the Company referencing the same notional amount. The interest rate swap transaction has the effect of fixing the annual interest rate payable on $150 million of the Company’s outstanding debt under it's existing credit facility to 1.89%, as of the effective date. The notional amounts of the interest rate swap agreement are used to measure interest to be paid or received and do not represent the amount of exposure to credit loss. This derivative instrument has been designated as a cash flow hedge of the variable interest payments on the related debt.
	Notwithstanding the terms of the interest rate swap transaction, the Company is ultimately obligated for all amounts due and payable under its existing Credit Agreement.
	The notional amount of the Company's derivative instruments are as follows:
		31-Mar-15		31-Dec-14
	Interest Rate swap	$	150,000,000	$	150,000,000
	The following table sets forth financial assets and liabilities measured at fair value in the consolidated balance sheets and the respective pricing levels to which the fair value measurements are classified within the fair value hierarchy. The Company uses the market approach to derive the value of its level 2 fair value measurements. Interest rate swaps are valued using publicized swap curves.
	Fair Value Measurements
	Quoted Prices with Other Observable Inputs (Level 2)
		31-Mar-15		31-Dec-14
	Financial assets:
	Interest Rate Swap Asset	$	—	$	—
	Financial Liabilities:
	Interest Rate Swap Liability (Other Accrued Liabilities)	$	3,307,392	$	1,475,702
	Based on loan balances as of March 31, 2015 and the effective date of July 31, 2015 of the interest rate swap, a one percent increase in the Company's borrowing rate would increase net interest expense paid by the Company on its borrowings by approximately $2.7 million dollars on an annual basis.

Equity

Equity	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Equity	Equity
	The decrease in common stock during the three months ended March 31, 2015, was primarily due to share repurchases of 1,406,595 shares pursuant to the Company's previously announced share repurchase plan which was partially offset by the the issuance of 834,750 shares of the Company’s common stock under the Company’s stock-based compensation plans. The Company recorded a cash dividend of $0.08 per share during the first quarter of 2015. The first quarter dividend of $23.6 million was declared on March 3, 2015, and was paid on April 17, 2015.
	Stock Split
	On December 5, 2014, the Company announced that its Board of Directors approved a two-for-one split of our outstanding shares of common stock to be effected in the form of a 100% stock dividend. On December 31, 2014, shareholders of record at the close of business on December 17, 2014, were issued one additional share of common stock for each share owned by such shareholder. The stock split increased the number of shares of common stock outstanding from approximately 147.6 million to approximately 295.2 million. Share and per-share amounts (including stock options and restricted stock) shown in the consolidated financial statements and related notes reflect the split. The total number of authorized common shares and the par value thereof was not changed by the split.

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies
	The Company is periodically involved in legal proceedings, legal actions and claims arising in the normal course of business, including proceedings relating to product liability, intellectual property, safety and health, employment and other matters. Such matters are subject to many uncertainties and outcomes are not predictable. The Company does not believe, however, that at the current time any of these matters constitute material pending legal proceedings that will have a material adverse effect on the financial position or future results of operations of the Company.

Segment_Reporting

Segment Reporting	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting
	The Company's automotive segment develops and manufactures electro-optic products, including: automatic-dimming rearview mirrors with and without electronic features for the automotive industry; non-auto dimming rearview automotive mirrors with and without electronic features; The Company also develops and manufactures variably dimming windows for the aerospace industry and fire protection products for the commercial construction industry, which are combined into the "Other" segment shown below.
		Three Months Ended March 31,
		2015		2014
	Revenue:
	Automotive Products	$	360,615,289	$	326,364,107
	Other	8,322,166		9,375,237
	Total	$	368,937,455	$	335,739,344
	Income from operations:
	Automotive Products	$	104,808,058	$	93,444,468
	Other	2,900,448		3,733,078
	Total	$	107,708,506	$	97,177,546

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The effective tax rate was 28.8% in the first quarter of 2015 compared to 32.6% for same quarter of 2014. Effective tax rates differ from statutory federal income tax rates, primarily due to the domestic manufacturing deduction, provisions for state and local income taxes and permanent tax differences. During calendar year 2014, the Company amended its tax return filings for calendar years 2010 through 2013 to claim incremental research and development tax credits.  During the first quarter of 2015, the Internal Revenue Service concluded its audit of the Company's original and amended filings for calendar years through 2012, and as a result, the Company realized additional benefits of approximately $3.9 million from the reversal of the uncertain tax position reserve related to the amended filings.

Stock_Split

Stock Split	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Stock Split	Equity
	The decrease in common stock during the three months ended March 31, 2015, was primarily due to share repurchases of 1,406,595 shares pursuant to the Company's previously announced share repurchase plan which was partially offset by the the issuance of 834,750 shares of the Company’s common stock under the Company’s stock-based compensation plans. The Company recorded a cash dividend of $0.08 per share during the first quarter of 2015. The first quarter dividend of $23.6 million was declared on March 3, 2015, and was paid on April 17, 2015.
	Stock Split
	On December 5, 2014, the Company announced that its Board of Directors approved a two-for-one split of our outstanding shares of common stock to be effected in the form of a 100% stock dividend. On December 31, 2014, shareholders of record at the close of business on December 17, 2014, were issued one additional share of common stock for each share owned by such shareholder. The stock split increased the number of shares of common stock outstanding from approximately 147.6 million to approximately 295.2 million. Share and per-share amounts (including stock options and restricted stock) shown in the consolidated financial statements and related notes reflect the split. The total number of authorized common shares and the par value thereof was not changed by the split.

Goodwill_and_Other_Intangible_1

Goodwill and Other Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	The patents and intangible assets and related change in carrying values are set forth in the table belows:
	As of March 31, 2015:
	Other Intangible Assets	Gross		Accumulated Amortization			Net		Assumed Useful Life
	Gentex Patents	$	30,363,189	$	(11,713,249	)	$	18,649,940	various
	Other Intangible Assets
	HomeLink®Trade Names and Trademarks	$	52,000,000	$	—		$	52,000,000	Indefinite
	HomeLink® Technology	180,000,000		(22,500,000		)	157,500,000		12 years
	Existing Customer Platforms	43,000,000		(6,450,000		)	36,550,000		10 years
	Exclusive Licensing Agreement	96,000,000		—			96,000,000		Indefinite
	Total Other Intangible Assets	$	371,000,000	$	(28,950,000	)	$	342,050,000
	Total Patents & Other Intangible Assets	$	401,363,189	$	(40,663,249	)	$	360,699,940
	As of December 31, 2014:
	Other Intangible Assets	Gross		Accumulated Amortization			Net		Assumed Useful Life
	Gentex Patents	$	30,132,116	$	(11,065,153	)	$	19,066,963	various
	HomeLink®Trade Names and Trademarks	$	52,000,000	$	—		$	52,000,000	Indefinite
	HomeLink® Technology	180,000,000		(18,750,000		)	$	161,250,000	12 years
	Existing Customer Platforms	43,000,000		(5,375,000		)	$	37,625,000	10 years
	Exclusive Licensing Agreement	96,000,000		—			$	96,000,000	Indefinite
	Total other identifiable intangible assets	$	371,000,000	$	(24,125,000	)	$	346,875,000
	Total Patents & Other Intangible Assets	$	401,132,116	$	(35,190,153	)	$	365,941,963

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2015
Investments [Abstract]
Investment Securities Stated at Fair Value	Assets or liabilities that have recurring fair value measurements are shown below as of March 31, 2015, and December 31, 2014:
	As of March 31, 2015:
				Fair Value Measurements at Reporting Date Using
		Total as of		Quoted Prices in		Significant			Significant
				Active Markets for		Other			Unobservable
				Identical Assets		Observable			Inputs
						Inputs
	Description	31-Mar-15		(Level 1)		(Level 2)			(Level 3)
	Cash & Cash Equivalents	$	549,911,648	$	549,911,648	$	—		$	—
	Short-Term Investments:
	Other	560		560		—			—
	Long-Term Investments:
	Common Stocks	24,161,865		24,161,865		—			—
	Mutual Funds – Equity	91,335,235		91,335,235		—			—
	Total	$	665,409,308	$	665,409,308	$	—		$	—
	As of December 31, 2014:
				Fair Value Measurements at Reporting Date Using
		Total as of		Quoted Prices in		Significant Other			Significant
				Active Markets for		Observable			Unobservable
				Identical Assets		Inputs			Inputs
	Description	31-Dec-14		(Level 1)		(Level 2)			(Level 3)
	Cash & Cash Equivalents	$	497,429,804	$	497,429,804	$	—		$	—
	Short-Term Investments:
	Other	1,021		1,021		—			—
	Long-Term Investments:
	Common Stocks	24,648,451		24,648,451		—			—
	Mutual Funds – Equity	89,994,116		89,994,116		—			—
	Total	$	612,073,392	$	612,073,392	$	—		$	—
Schedule of Amortized Cost, Unrealized Gains And Losses, And Market Value of Investment Securities	The amortized cost, unrealized gains and losses, and market value of investment securities are shown as of March 31, 2015, and December 31, 2014:
	As of March 31, 2015:
				Unrealized
		Cost		Gains		Losses			Market Value
	Short-Term Investments:
	Other	$	560	$	—	$	—		$	560
	Long-Term Investments:
	Common Stocks	18,804,767		5,825,050		(467,952		)	24,161,865
	Mutual Funds – Equity	80,549,522		11,109,462		(323,749		)	91,335,235
	Total	$	99,354,849	$	16,934,512	$	(791,701	)	$	115,497,660
	As of December 31, 2014:
				Unrealized
		Cost		Gains		Losses			Market Value
	Short-Term Investments:
	Other	1,021		—		—			1,021
	Long-Term Investments:
	Common Stocks	$	17,069,742	$	7,933,717	$	(355,008	)	$	24,648,451
	Mutual Funds – Equity	80,852,329		9,922,204		(780,417		)	89,994,116
	Total	$	97,923,092	$	17,855,921	$	(1,135,425	)	$	114,643,588
Schedule of Unrealized Loss on Investments	Unrealized losses on investments as of March 31, 2015, are as follows:
		Aggregate Unrealized Losses		Aggregate Fair Value
	Less than one year	$	791,701	$	15,894,733
	Unrealized losses on investments as of December 31, 2014, are as follows:
		Aggregate Unrealized Losses		Aggregate Fair Value
	Less than one year	$	1,135,425	$	19,972,258

Inventories_Tables

Inventories (Tables)	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories consisted of the following at the respective balance sheet dates:
		March 31, 2015		December 31, 2014
	Raw materials	$	91,275,645	$	90,780,320
	Work-in-process	24,207,804		24,135,944
	Finished goods	30,080,500		26,841,620
	Total Inventory	$	145,563,949	$	141,757,884

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Schedule of Earnings Per Share Basic And Diluted	The following table reconciles the numerators and denominators used in the calculation of basic and diluted earnings per share (EPS), adjusted for the 2 for 1 stock split effected in the form of a 100% stock dividend issued on December 31, 2014:
		Three Months Ended March 31,
		2015		2014
	Numerators:
	Numerator for both basic and diluted EPS, net income	$	77,183,441	$	68,566,071
	Denominators:
	Denominator for basic EPS, weighted-average shares outstanding	295,031,431		289,836,812
	Potentially dilutive shares resulting from stock plans	3,562,712		3,600,202
	Denominator for diluted EPS	298,594,143		293,437,014
	Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive	1,184,635		1,188,830

StockBased_Compensation_Plans_

Stock-Based Compensation Plans (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted-Average Assumptions For The Employee Stock Option Plan	The fair value of each option grant in the employee stock option plan was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions for the indicated periods:
		Three Months Ended March 31,
		2015		2014
	Dividend Yield (1)	2.14	%	2.33	%
	Expected volatility (2)	36.8	%	40.36	%
	Risk-free interest rate (3)	1.37	%	1.74	%
	Expected term of options (years) (4)	4.29		3.95
	Weighted-avg. grant date fair value	$4.76		$4.27
	(1)Represents the Company’s estimated cash dividend yield over the expected term of option grant.
	(2)	Amount is determined based on analysis of historical price volatility of the Company’s common stock. The expected volatility is based on the daily percentage change in the price of the stock over a period equal to the expected term of the option grant.
	(3)	Represents the U.S. Treasury yield over the expected term of the option grant.
	(4)	Represents the period of time that options granted are expected to be outstanding. Based on analysis of historical option exercise activity, the Company has determined that all employee groups exhibit similar exercise and post-vesting termination behavior.

Comprehensive_Income_Tables

Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Schedule of net changes in the Company's accumulated other comprehensive income by component	The following table presents the net changes in the Company's accumulated other comprehensive income by component: (All amounts shown are net of tax).
		Three Months Ended March 31,
		2015				2014
	Foreign currency translation adjustments:
	Balance at beginning of period	$	1,403,899			$	2,507,922
	Other Comprehensive (loss) income before reclassifications	(942,974		)		(91,250		)
	Amounts reclassified from accumulated other comprehensive income	—				—
	Net current-period change	(942,974		)		(91,250		)
	Balance at end of period	460,925				2,416,672
	Unrealized gains on available-for-sale securities:
	Balance at beginning of period	10,868,322				19,467,441
	Other Comprehensive income (loss) before reclassifications	(2,073,471		)		864,910
	Amounts reclassified from accumulated other comprehensive income	1,697,976				(3,265,224		)
	Net current-period change	(375,495		)		(2,400,314		)
	Balance at end of period	10,492,827				17,067,127
	Unrealized gains (losses) on derivatives:
	Balance at beginning of period	(959,206		)		—
	Other comprehensive income (loss) before reclassifications	—				—
	Amounts reclassified from accumulated other comprehensive income	(1,190,599		)		—
	Net current-period change	(1,190,599		)		—
	Balance at end of period	(2,149,805		)		—
	Accumulated other comprehensive income, end of period	$	8,803,947			$	19,483,799
Schedule of reclassifications out of other comprehensive income	The following table presents details of reclassifications out of other comprehensive income for the three months ended March 31, 2015 and 2014.
	Details about Accumulated Other Comprehensive Income Components		Amounts Reclassified from Other Comprehensive Income							Affected Line item in the Statement of Consolidated Income
			Three Months Ended March 31,
			2015				2014
	Unrealized gains on available-for-sale securities
	Realized gain on sale of securities		$	2,612,271			$	5,023,421		Other, net
	Provision for Income Taxes		(914,295		)		(1,758,197		)	Provision for Income Taxes
	Total reclassifications for the period		$	1,697,976			$	3,265,224		Net of tax

Debt_and_Financing_Arrangement1

Debt and Financing Arrangements (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Schedule of notional amount of the Company's derivative instruments	The notional amount of the Company's derivative instruments are as follows:
		31-Mar-15		31-Dec-14
	Interest Rate swap	$	150,000,000	$	150,000,000
Schedule of financial assets and liabilities measured at fair value in the consolidated balance sheets	The Company uses the market approach to derive the value of its level 2 fair value measurements. Interest rate swaps are valued using publicized swap curves.
	Fair Value Measurements
	Quoted Prices with Other Observable Inputs (Level 2)
		31-Mar-15		31-Dec-14
	Financial assets:
	Interest Rate Swap Asset	$	—	$	—
	Financial Liabilities:
	Interest Rate Swap Liability (Other Accrued Liabilities)	$	3,307,392	$	1,475,702

Segment_Reporting_Tables

Segment Reporting (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Schedule of Automotive and Other Segment Reporting	The Company also develops and manufactures variably dimming windows for the aerospace industry and fire protection products for the commercial construction industry, which are combined into the "Other" segment shown below.
		Three Months Ended March 31,
		2015		2014
	Revenue:
	Automotive Products	$	360,615,289	$	326,364,107
	Other	8,322,166		9,375,237
	Total	$	368,937,455	$	335,739,344
	Income from operations:
	Automotive Products	$	104,808,058	$	93,444,468
	Other	2,900,448		3,733,078
	Total	$	107,708,506	$	97,177,546

Goodwill_and_Other_Intangible_2

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
HomeLinkB.
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 | HomeLinkB.
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	5,500,000
Intangible Assets [Member] | HomeLinkB.
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.

Goodwill_and_Other_Intangible_3

Goodwill and Other Intangible Assets (Schedule of Intangible Assets) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible assets, net	342,050,000	346,875,000	[1]
Gentex Patents
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	30,363,189	30,132,116
Finite-lived intangible assets, accumulated amortization	-11,713,249	-11,065,153
Finite-lived intangible assets, net	18,649,940	19,066,963
Patents and Other Intangible Assets [Member]
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, accumulated amortization	-40,663,249	-35,190,153
Intangible assets, gross	401,363,189	401,132,116
Intangible assets, net	360,699,940	365,941,963
HomeLinkB.
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, accumulated amortization	-28,950,000	-24,125,000
Intangible assets, gross	371,000,000	371,000,000
Intangible assets, net	342,050,000	346,875,000
HomeLinkB. | 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	-22,500,000	-18,750,000
Finite-lived intangible assets, net	157,500,000	161,250,000
HomeLinkB. | Homelink Technology | Minimum [Member]
Schedule of Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	12 years 0 days	12 years
HomeLinkB. | 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	-6,450,000	-5,375,000
Finite-lived intangible assets, net	36,550,000	37,625,000
Finite-lived intangible asset, useful life	10 years	10 years
HomeLinkB. | 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
HomeLinkB. | 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, 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.

Investments_Schedule_of_Amorti

Investments (Schedule of Amortized Cost, Unrealized Gains And Losses, And Market Value of Investment Securities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	$549,911,648	$497,429,804
Cost	99,354,849	97,923,092
Unrealized Gains	16,934,512	17,855,921
Unrealized Losses	-791,701	-1,135,425
Market Value	115,497,660	114,643,588
Investments and Cash	665,409,308	612,073,392
Short-term Investments [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	560	1,021
Unrealized Gains	0	0
Unrealized Losses	0	0
Market Value	560	1,021
Long-Term Investments [Member] | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Cost	18,804,767	17,069,742
Unrealized Gains	5,825,050	7,933,717
Unrealized Losses	-467,952	-355,008
Market Value	24,161,865	24,648,451
Long-Term Investments [Member] | Mutual Funds b Equity
Schedule of Available-for-sale Securities [Line Items]
Cost	80,549,522	80,852,329
Unrealized Gains	11,109,462	9,922,204
Unrealized Losses	-323,749	-780,417
Market Value	91,335,235	89,994,116
Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	549,911,648	497,429,804
Investments and Cash	665,409,308	612,073,392
Fair Value, Inputs, Level 1 [Member] | Short-term Investments [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	560	1,021
Fair Value, Inputs, Level 1 [Member] | Long-Term Investments [Member] | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Market Value	24,161,865	24,648,451
Fair Value, Inputs, Level 1 [Member] | Long-Term Investments [Member] | Mutual Funds b Equity
Schedule of Available-for-sale Securities [Line Items]
Market Value	91,335,235	89,994,116
Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	0	0
Fair Value, Inputs, Level 2 [Member] | Short-term Investments [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 2 [Member] | Long-Term Investments [Member] | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 2 [Member] | Long-Term Investments [Member] | Mutual Funds b Equity
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash & Cash Equivalents	0	0
Investments and Cash	0	0
Fair Value, Inputs, Level 3 [Member] | Short-term Investments [Member] | Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member] | Long-Term Investments [Member] | Common Stock
Schedule of Available-for-sale Securities [Line Items]
Market Value	0	0
Fair Value, Inputs, Level 3 [Member] | Long-Term Investments [Member] | Mutual Funds b Equity
Schedule of Available-for-sale Securities [Line Items]
Market Value	$0	$0

Investments_Schedule_of_Unreal

Investments (Schedule of Unrealized Loss on Investments) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Investments [Abstract]
Aggregate Unrealized Losses, Less than one year	$791,701	$1,135,425
Aggregate Fair Value, Less than one year	15,894,733	19,972,258
Equity investment losses were considered to be other than temporary	$0

Inventories_Schedule_of_Invent

Inventories (Schedule of Inventories) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw materials	$91,275,645	$90,780,320
Work-in-process	24,207,804	24,135,944
Finished goods	30,080,500	26,841,620
Total Inventory	$145,563,949	$141,757,884	[1]
[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.

Earnings_Per_Share_Schedule_of

Earnings Per Share (Schedule of Earnings Per Share, Basic And Diluted) (Details) (USD $)	3 Months Ended		0 Months Ended	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 05, 2014	Dec. 31, 2014
Numerators [Abstract]
Numerator for both basic and diluted EPS, net income	$77,183,441	$68,566,071
Denominators [Abstract]
Denominator for basic EPS, weighted-average shares outstanding	295,031,431	289,836,812
Potentially dilutive shares resulting from stock plans	3,562,712	3,600,202
Denominator for diluted EPS	298,594,143	293,437,014
Shares related to stock plans not included in diluted average common shares outstanding because their effect would be anti-dilutive	1,184,635	1,188,830
Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock split, conversion ratio			2	2
Stock split, stock dividend			100.00%	100.00%

StockBased_Compensation_Plans_1

Stock-Based Compensation Plans (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	31-May-14
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense for share-based payments	$4,846,051
Compensation cost capitalized as part of inventory	239,947
Employee Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares)		24,000,000
Unrecognized compensation cost	25,868,764
Employee Stock Option Plan [Member] | Minimum [Member]
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 [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	5 years
Option expiration period	7 years
Non-Employee Director Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period	6 months
Option expiration period	10 years
Unrecognized compensation cost	0
Options granted (in shares)	266,000
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved (in shares)	2,000,000
ESPP discount rate	85.00%
ESPP discount rate recognized as compensation expense	15.00%
Restricted Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	4,000,000
Restricted period, maximum, in years	10 years
Unearned stock-based compensation	11,753,501
Amortization expense	$967,900
Equity Incentive Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans (in plans)	4
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of plans (in plans)	2

StockBased_Compensation_Plans_2

Stock-Based Compensation Plans (Weighted-Average Assumptions for the ESOP) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Dividend yield	2.14%	2.33%
Expected volatility	36.80%	40.36%
Risk-free interest rate	1.37%	1.74%
Expected term of options	4 years 105 days	3 years 11 months 12 days
Weighted-avg. grant-date fair value (in dollars per share)	$4.76	$4.27

Comprehensive_Income_AOCI_Roll

Comprehensive Income (AOCI Rollforward) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$11,313,015	[1]
Comprehensive Income	74,674,373		66,074,507
Balance at end of period	8,803,947		19,483,799
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	1,403,899		2,507,922
Other Comprehensive (loss) income before reclassifications	-942,974		-91,250
Amounts reclassified from accumulated other comprehensive income	0		0
Comprehensive Income	-942,974		-91,250
Balance at end of period	460,925		2,416,672
Unrealized gains on available-for-sale securities:
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	10,868,322		19,467,441
Other Comprehensive (loss) income before reclassifications	-2,073,471		864,910
Amounts reclassified from accumulated other comprehensive income	1,697,976		-3,265,224
Comprehensive Income	-375,495		-2,400,314
Balance at end of period	10,492,827		17,067,127
Unrealized gains (losses) on derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	-959,206		0
Other Comprehensive (loss) income before reclassifications	0		0
Amounts reclassified from accumulated other comprehensive income	-1,190,599		0
Comprehensive Income	-1,190,599		0
Balance at end of period	($2,149,805)		$0
[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.

Comprehensive_Income_Reclassif

Comprehensive Income (Reclassification Out of Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Provision for Income Taxes	($31,234,449)	($33,126,019)
Amounts Reclassified from Other Comprehensive Income | Unrealized gains on available-for-sale securities:
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Realized gain on sale of securities	2,612,271	5,023,421
Provision for Income Taxes	-914,295	-1,758,197
Total reclassifications for the period	$1,697,976	$3,265,224

Debt_and_Financing_Arrangement2

Debt and Financing Arrangements (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014		Oct. 01, 2014	Sep. 27, 2013
Debt Instrument [Line Items]
Long-term debt	$256,250,000		$258,125,000	[1]
Financial Liabilities:
Effect of 1% in increase on borrowing rate	2,700,000
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Amount of hedged item					150,000,000
Notional amount of derivative	150,000,000		150,000,000		150,000,000
Fixed interest rate of derivative					1.89%
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets:
Interest Rate Swap Asset	0		0
Financial Liabilities:
Interest Rate Swap Liability (Other Accrued Liabilities)	3,307,392		1,475,702
Other, Net [Member]
Debt Instrument [Line Items]
Payments of financing costs	800,000	900,000
LIBOR Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.18%
Term Loan and Revolving Facility [Member]
Debt Instrument [Line Items]
Partial repayment of debt	1,900,000
Credit Agreement [Member]
Debt Instrument [Line Items]
Additional principal amount available						75,000,000
Revolving Facility [Member]
Debt Instrument [Line Items]
Principal amount						150,000,000
Long-term debt	125,000,000
Available borrowing capacity	25,000,000
Term Loan [Member]
Debt Instrument [Line Items]
Principal amount						150,000,000
Long-term debt	138,800,000
Annual principal repayments	7,500,000
Swing Loans [Member]
Debt Instrument [Line Items]
Additional principal amount available						20,000,000
Letters of Credit [Member]
Debt Instrument [Line Items]
Additional principal amount available						$20,000,000
[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.

Equity_Details

Equity (Details) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Equity [Abstract]
Stock repurchased (in shares)	1,406,595
Common stock issued under stock compensation plan (in shares)	834,750
Dividends declared (in dollars per share)	$0.08	$0.07
Dividends declared	$23.60

Segment_Reporting_Schedule_Of_

Segment Reporting (Schedule Of Automotive And Other Segment Reporting) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Revenue	$368,937,455	$335,739,344
Income from operations	107,708,506	97,177,546
Automotive Products
Segment Reporting Information [Line Items]
Revenue	360,615,289	326,364,107
Income from operations	104,808,058	93,444,468
Other
Segment Reporting Information [Line Items]
Revenue	8,322,166	9,375,237
Income from operations	$2,900,448	$3,733,078

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	28.80%	32.60%
Incremental research & development tax credits	$3.90

Stock_Split_Details

Stock Split (Details) (Common Stock)	0 Months Ended	12 Months Ended
	Dec. 05, 2014	Dec. 31, 2014	Dec. 17, 2014
Common Stock
Class of Stock [Line Items]
Stock split, conversion ratio	2	2
Stock split, stock dividend	100.00%	100.00%
Common stock split, additional shares issued for every share held (in shares)			1
Common stock, shares outstanding (in shares)		295,200,000	147,600,000