Segment Reporting (Schedule Of Automotive And Other Segment Reporting) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 460,253,433	$ 438,627,786	$ 1,380,654,978	$ 1,335,302,109
Income from operations	127,427,911	129,072,652	382,626,248	389,364,286
Automotive Products
Segment Reporting Information [Line Items]
Revenue	449,184,447	428,161,863	1,348,395,245	1,307,736,698
Income from operations	124,351,499	125,817,994	373,071,852	381,545,762
Other
Segment Reporting Information [Line Items]
Revenue	11,068,986	10,465,923	32,259,733	27,565,411
Income from operations	$ 3,076,412	$ 3,254,658	$ 9,554,396	$ 7,818,524