Segment Reporting (Schedule of Automotive and Other Segment Reporting) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 419,913,000	$ 429,643,000	$ 423,801,000	$ 405,568,000	$ 405,593,000	$ 389,829,000	$ 379,258,000	$ 368,937,000	$ 1,678,924,756	$ 1,543,617,706	$ 1,375,501,159
Income (Loss) from Operations	127,936,000	$ 134,212,000	$ 128,746,000	$ 120,849,000	126,662,000	$ 116,263,000	$ 108,133,000	$ 107,709,000	511,742,935	458,766,439	398,834,174
Assets	2,309,619,833				2,148,672,928				2,309,619,833	2,148,672,928	2,022,540,029
Depreciation & Amortization									88,587,430	80,599,167	77,376,305
Capital Expenditures									120,955,614	97,941,762	72,518,987
Corporate
Segment Reporting Information [Line Items]
Assets	842,246,344				724,816,255				842,246,344	724,816,255	680,082,682
Depreciation & Amortization									1,729,886	1,366,927	1,733,880
Capital Expenditures									20,944,269	147,996	1,341,168
Automotive Products
Segment Reporting Information [Line Items]
Revenues									1,639,692,243	1,506,872,004	1,340,122,274
Income (Loss) from Operations									497,753,966	445,067,511	386,762,986
Assets	1,457,989,335				1,414,426,679				1,457,989,335	1,414,426,679	1,333,615,389
Depreciation & Amortization									86,567,248	78,925,332	75,320,999
Capital Expenditures									99,811,083	97,632,519	71,032,115
Other
Segment Reporting Information [Line Items]
Revenues									39,232,514	36,745,702	35,378,885
Income (Loss) from Operations									13,988,969	13,698,928	12,071,188
Assets	$ 9,384,154				$ 9,429,994				9,384,154	9,429,994	8,841,958
Depreciation & Amortization									290,296	306,908	321,426
Capital Expenditures									200,262	161,247	145,704
United States | Automotive Products
Segment Reporting Information [Line Items]
Revenues									554,945,912	494,876,354	444,921,897
Germany | Automotive Products
Segment Reporting Information [Line Items]
Revenues									328,208,190	295,044,988	262,505,346
Japan | Automotive Products
Segment Reporting Information [Line Items]
Revenues									154,005,299	148,632,237	133,758,799
Other | Automotive Products
Segment Reporting Information [Line Items]
Revenues									$ 602,532,841	$ 568,318,425	$ 498,936,232