Condensed Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 124,202,115	$ 100,810,704
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	33,310,248	29,591,073
(Gain) loss on disposal of assets	838,359	662,402
(Gain) loss on sale of investments	(7,390,376)	(4,379,689)
Impairment loss on available-for-sale securities	0	0
Deferred income taxes	3,027,961	4,164,643
Stock-based compensation expense related to employee stock options, employee stock purchases and restricted stock	10,184,719	7,669,990
Excess tax benefits from stock-based compensation	(3,361,960)	(585,954)
Change in operating assets and liabilities:
Accounts receivable, net	(34,391,598)	(35,522,370)
Inventories	(50,402,115)	(38,497,371)
Prepaid expenses and other	6,319,685	3,686,589
Accounts payable	29,862,133	22,648,952
Accrued liabilities, excluding dividends declared	13,232,767	1,859,735
Net cash provided by (used for) operating activities	125,431,938	92,108,704
CASH FLOWS FROM INVESTING ACTIVITIES:
Plant and equipment additions	(84,994,919)	(29,126,357)
Proceeds from sale of plant and equipment	177,132	480,460
(Increase) decrease in investments	31,358,531	(78,123,603)
(Increase) decrease in other assets	1,560,369	(4,095,559)
Net cash provided by (used for) investing activities	(51,898,887)	(110,865,059)
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance of common stock from stock plan transactions	21,815,871	31,734,568
Cash dividends paid	(49,955,251)	(45,954,715)
Excess tax benefits from stock-based compensation	3,361,960	585,954
Net cash provided by (used for) financing activities	(24,777,420)	(13,634,193)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	48,755,631	(32,390,548)
CASH AND CASH EQUIVALENTS, beginning of period	348,349,773	336,108,446
CASH AND CASH EQUIVALENTS, end of period	$ 397,105,404	$ 303,717,898

Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.1)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

-Number 210

-Section 02

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7

-Footnote 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 8, 9

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 7, 26

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016