Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Operating activities:
Net income	$ 173,860		$ 154,329
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and intangibles	47,477		44,179
Amortization of debt discount and issuance costs	520		496
Excess tax benefit from stock options exercised	(17,850)		(10,788)
Deferred income taxes	(3,796)		(2,691)
Share-based compensation programs	5,096		5,597
Other	1,526		1,462
Changes in operating assets and liabilities:
Accounts receivable	(13,016)		(31,844)
Inventory	(21,994)		(19,515)
Accounts payable	104,376		37,888
Income taxes payable	69,922		60,859
Other	(572)		(13,628)
Net cash provided by operating activities	345,549		226,344
Investing activities:
Purchases of property and equipment	(83,085)		(73,484)
Proceeds from sale of property and equipment	287		355
Payments received on notes receivable	900		1,029
Net cash used in investing activities	(81,898)		(72,100)
Financing activities:
Principal payments on capital leases	(18)		(145)
Repurchases of common stock	(22,067)		(227,930)
Excess tax benefit from stock options exercised	17,850		10,788
Net proceeds from issuance of common stock	21,097		20,325
Net cash provided by (used in) financing activities	16,862		(196,962)
Net increase (decrease) in cash and cash equivalents	280,513		(42,718)
Cash and cash equivalents at beginning of the period	231,318	[1]	248,128
Cash and cash equivalents at end of the period	511,831		205,410
Supplemental disclosures of cash flow information:
Income taxes paid	33,331		29,158
Interest paid, net of capitalized interest	$ 22,419		$ 23,764

[1] The balance sheet at December 31, 2013, 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.