Segment Reporting (Schedule of Automotive and Other Segment Reporting) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 453,409,000	$ 460,253,000	$ 454,981,000	$ 465,420,000	$ 459,570,000	$ 438,628,000	$ 443,139,000	$ 453,535,000	$ 1,834,063,697	$ 1,794,872,578	$ 1,678,924,756
Income (Loss) from Operations	125,499,000	$ 127,428,000	$ 126,683,000	$ 128,515,000	133,994,000	$ 129,073,000	$ 125,865,000	$ 134,427,000	508,125,547	523,358,352	511,742,935
Assets	2,085,434,068				2,352,053,912				2,085,434,068	2,352,053,912	2,309,619,833
Depreciation & Amortization									102,186,814	99,570,908	88,587,430
Capital Expenditures									85,990,570	104,040,919	120,955,614
Corporate
Segment Reporting Information [Line Items]
Assets	621,190,035				870,415,748				621,190,035	870,415,748	842,246,344
Depreciation & Amortization									4,484,918	3,891,873	1,729,886
Capital Expenditures									205,621	21,166,986	20,944,269
Automotive Products
Segment Reporting Information [Line Items]
Revenues									1,791,198,296	1,758,127,468	1,639,692,243
Income (Loss) from Operations									495,471,799	512,895,699	497,753,966
Automotive Products | Operating Segments
Segment Reporting Information [Line Items]
Assets	1,449,910,935				1,472,061,650				1,449,910,935	1,472,061,650	1,457,989,335
Depreciation & Amortization									97,279,052	95,378,100	86,567,248
Capital Expenditures									84,337,455	82,703,576	99,811,083
Other
Segment Reporting Information [Line Items]
Revenues									42,865,401	36,745,110	39,232,514
Income (Loss) from Operations									12,653,748	10,462,653	13,988,969
Other | Operating Segments
Segment Reporting Information [Line Items]
Assets	$ 14,333,098				$ 9,576,514				14,333,098	9,576,514	9,384,154
Depreciation & Amortization									422,844	300,935	290,296
Capital Expenditures									1,447,494	170,357	200,262
U.S. | Automotive Products
Segment Reporting Information [Line Items]
Revenues									583,672,971	567,492,812	554,945,912
Germany | Automotive Products
Segment Reporting Information [Line Items]
Revenues									333,002,878	351,123,204	328,208,190
Japan | Automotive Products
Segment Reporting Information [Line Items]
Revenues									209,311,790	185,261,067	154,005,299
Other | Automotive Products
Segment Reporting Information [Line Items]
Revenues									$ 665,210,657	$ 654,250,385	$ 602,532,841