Segment Reporting (Schedule Of Automotive And Other Segment Reporting) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenue	$ 454,981,440	$ 443,139,073	$ 920,401,545	$ 896,674,323
Income from operations	126,683,004	125,864,514	255,198,337	260,291,634
Automotive Products
Segment Reporting Information [Line Items]
Revenue	444,245,425	433,922,260	899,210,798	879,574,835
Income from operations	123,758,195	123,222,811	248,720,353	255,727,768
Other
Segment Reporting Information [Line Items]
Revenue	10,736,015	9,216,813	21,190,747	17,099,488
Income from operations	$ 2,924,809	$ 2,641,703	$ 6,477,984	$ 4,563,866