Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Operating activities:
Net income	$ 331,456		$ 293,612
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and intangibles	89,682		88,230
Amortization of debt discount and issuance costs	1,000		837
Excess tax benefit from stock options exercised	(18,681)		(23,692)
Deferred income taxes	(80)		4,375
Share-based compensation programs	11,174		10,891
Other	3,117		4,075
Changes in operating assets and liabilities:
Accounts receivable	(56,681)		(20,802)
Inventory	(69,046)		(159,591)
Accounts payable	129,747		420,554
Income taxes payable	23,823		47,159
Other	(6,099)		25,810
Net cash provided by operating activities	439,412		691,458
Investing activities:
Purchases of property and equipment	(176,577)		(151,327)
Proceeds from sale of property and equipment	678		2,071
Payments received on notes receivable	2,166		2,100
Net cash used in investing activities	(173,733)		(147,156)
Financing activities:
Proceeds from the issuance of long-term debt	299,976
Payment of debt issuance costs	(1,879)
Principal payments on capital leases	(189)		(367)
Repurchases of common stock	(501,914)		(594,450)
Excess tax benefit from stock options exercised	18,681		23,692
Net proceeds from issuance of common stock	37,448		32,988
Net cash used in financing activities	(147,877)		(538,137)
Net increase in cash and cash equivalents	117,802		6,165
Cash and cash equivalents at beginning of period	248,128	[1]	361,552
Cash and cash equivalents at end of period	365,930		367,717
Supplemental disclosures of cash flow information:
Income taxes paid	170,100		125,575
Interest paid, net of capitalized interest	$ 21,706		$ 17,718

[1] The balance sheet at December 31, 2012, has been derived from the audited consolidated financial statements at that date, but does not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements.