Unaudited Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 87,131,768	$ 213,239,036
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	53,437,698	53,296,388
(Gain) on disposal of assets	(155,229)	(95,658)
Loss on disposal of assets	88,357	340,070
(Gain) on sale of investments	(1,023,683)	(218,981)
Loss on sale of investments	72,871	0
Change in deferred income taxes	(2,176,462)	196,133
Stock-based compensation expense related to employee stock options, employee stock purchases and restricted stock	15,960,362	10,139,148
Change in operating assets and liabilities:
Accounts receivable, net	64,981,864	(12,888,533)
Inventories	(10,710,548)	187,136
Prepaid expenses and other	14,230,026	(2,311,576)
Accounts payable	(37,452,944)	(2,769,229)
Accrued liabilities, excluding dividends declared and short-term debt	6,068,104	14,353,360
Net cash provided by operating activities	190,452,184	273,467,294
Activity in available-for-sale securities:
Sales proceeds	5,607,634	28,845,319
Maturities and calls	90,017,368	9,714,000
Purchases	(52,650,769)	(40,298,297)
Plant and equipment additions	(28,828,066)	(45,504,667)
Proceeds from sale of plant and equipment	200,475	227,738
Acquisition of businesses, net of cash acquired	(7,031,827)	0
Decrease in other assets	(3,886,518)	(1,022,057)
Net cash (used for) investing activities	3,428,297	(48,037,964)
CASH FLOWS (USED FOR) FINANCING ACTIVITIES:
Proceeds from borrowings on Credit Agreement	75,000,000	0
Issuance of common stock from stock plan transactions	15,710,692	41,934,814
Cash dividends paid	(58,281,727)	(57,918,158)
Repurchases of common stock	(178,819,584)	(166,138,372)
Net cash (used for) financing activities	(146,390,619)	(182,121,716)
NET INCREASE IN CASH AND CASH EQUIVALENTS	47,489,862	43,307,614
CASH AND CASH EQUIVALENTS, beginning of period	296,321,622	217,025,278
CASH AND CASH EQUIVALENTS, end of period	$ 343,811,484	$ 260,332,892