Unaudited Condensed Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 276,617,836	$ 204,224,370
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	75,105,881	78,489,026
(Gain) on disposal of assets	(459,528)	(281,542)
Loss on disposal of assets	213,430	146,195
(Gain) on sale of investments	(969,971)	(1,504,757)
Loss on sale of investments	192,346	143,370
Change in deferred income taxes	(20,269,706)	(9,559,993)
Stock-based compensation expense related to employee stock options, employee stock purchases and restricted stock	20,114,921	23,266,906
Change in operating assets and liabilities:
Accounts receivable, net	43,704,625	(32,832,997)
Inventories	(66,308,038)	15,659,539
Prepaid expenses and other	(45,504,501)	8,934,297
Accounts payable	15,748,219	(7,389,582)
Accrued liabilities, excluding dividends declared and short-term debt	1,195,477	49,749,418
Net cash provided by operating activities	299,380,991	329,044,250
Activity in available-for-sale securities:
Sales proceeds	34,250,068	15,559,590
Maturities and calls	26,110,000	117,172,368
Purchases	(86,228,584)	(59,933,780)
Plant and equipment additions	(44,357,786)	(37,048,073)
Proceeds from sale of plant and equipment	2,550,805	331,465
Acquisition of businesses, net of cash acquired	(12,023,440)	(8,043,217)
Increase in other assets	(2,763,847)	(3,326,783)
Net cash (used for) provided by investing activities	(82,462,784)	24,711,570
CASH FLOWS (USED FOR) FINANCING ACTIVITIES:
Proceeds from borrowings on Credit Agreement	0	75,000,000
Repayment of borrowings on Credit Agreement	0	(50,000,000)
Issuance of common stock from stock plan transactions	20,773,874	23,677,181
Cash dividends paid	(86,902,257)	(87,774,635)
Repurchases of common stock	(304,195,755)	(210,480,446)
Net cash (used for) financing activities	(370,324,138)	(249,577,900)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(153,405,931)	104,177,920
CASH AND CASH EQUIVALENTS, beginning of period	423,371,036	296,321,622
CASH AND CASH EQUIVALENTS, end of period	$ 269,965,105	$ 400,499,542