Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 360,797,232	$ 347,563,621	$ 424,683,939
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	99,112,019	104,739,900	104,702,974
Gain on disposal of assets	(488,750)	(311,510)	(155,150)
Loss on disposal of assets	230,933	162,553	588,941
Gain on sale of investments	(1,379,538)	(3,163,164)	(660,643)
Loss on sale of investments	307,490	1,064,508	176,360
Deferred income taxes	(41,694,751)	(15,419,722)	(3,358,537)
Stock based compensation expense related to employee stock options, employee stock purchases and restricted stock	27,421,645	30,797,327	21,671,192
Change in operating assets and liabilities:
Accounts receivable	35,135,429	(49,290,457)	(21,872,527)
Inventories	(89,975,599)	22,725,798	(23,660,256)
Prepaid expenses and other	(20,241,994)	10,493,993	(3,646,457)
Accounts payable	7,266,309	(12,854,038)	4,743,601
Accrued liabilities	(14,322,863)	27,982,962	2,753,427
Net cash flows from operating activities	362,167,562	464,491,771	505,966,864
Activity in available-for-sale securities:
Sales proceeds	56,237,427	24,455,695	57,139,135
Maturities and calls	27,690,000	142,547,368	125,013,589
Purchases	(113,204,199)	(73,719,189)	(153,257,603)
Plant and equipment additions	(68,835,047)	(51,706,541)	(84,580,255)
Proceeds from sale of plant and equipment	2,577,855	383,429	2,001,315
Acquisition of businesses, net of cash acquired	(12,071,546)	(11,216,927)	0
Increase in other assets	(5,501,445)	(4,327,398)	(3,027,263)
Net cash (used for) from investing activities	(113,106,955)	26,416,437	(56,711,082)
CASH FLOWS USED FOR FINANCING ACTIVITIES:
Proceeds from borrowings on Credit Agreement	0	75,000,000	0
Repayment of borrowings on Credit Agreement	0	(75,000,000)	0
Issuance of common stock from stock plan transactions	29,808,787	41,803,640	77,821,151
Cash dividends paid	(115,285,625)	(117,181,928)	(116,309,197)
Repurchases of common stock	(324,643,135)	(288,480,506)	(331,471,392)
Net cash used for financing activities	(410,119,973)	(363,858,794)	(369,959,438)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(161,059,366)	127,049,414	79,296,344
CASH AND CASH EQUIVALENTS, Beginning of year	423,371,036	296,321,622	217,025,278
CASH AND CASH EQUIVALENTS, End of year	$ 262,311,670	$ 423,371,036	$ 296,321,622