Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014
Operating activities:
Net income	$ 446,372		$ 379,507
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and intangibles	106,007		95,004
Amortization of debt discount and issuance costs	1,051		1,041
Excess tax benefit from stock options exercised	(32,947)		(23,849)
Deferred income taxes	(15,326)		(12,686)
Share-based compensation programs	11,304		12,137
Other	2,594		2,718
Changes in operating assets and liabilities:
Accounts receivable	(34,199)		(28,422)
Inventory	(6,186)		(87,734)
Accounts payable	118,804		245,761
Income taxes payable	79,172		39,412
Other	21,807		32,636
Net cash provided by operating activities	698,453		655,525
Investing activities:
Purchases of property and equipment	(186,531)		(194,929)
Proceeds from sale of property and equipment	1,608		789
Payments received on notes receivable	1,981		1,835
Net cash used in investing activities	(182,942)		(192,305)
Financing activities:
Principal payments on capital leases	(25)		(36)
Repurchases of common stock	(574,972)		(299,655)
Excess tax benefit from stock options exercised	32,947		23,849
Net proceeds from issuance of common stock	36,021		34,735
Net cash used in financing activities	(506,029)		(241,107)
Net increase in cash and cash equivalents	9,482		222,113
Cash and cash equivalents at beginning of the period	250,560	[1]	231,318
Cash and cash equivalents at end of the period	260,042		453,431
Supplemental disclosures of cash flow information:
Income taxes paid	194,715		189,944
Interest paid, net of capitalized interest	$ 27,711		$ 25,190

[1] The balance sheet at December 31, 2014, has been derived from the audited consolidated financial statements at that date, but does not include all of the information and footnotes required by United States generally accepted accounting principles for complete financial statements.