Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Operating activities:
Net income	$ 1,133,804	$ 1,037,691		$ 931,216
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and intangibles	233,845	217,866		210,256
Amortization of debt discount and issuance costs	2,871	2,451		2,106
Deferred income taxes	(4,593)	10,394		(22,650)
Share-based compensation programs	19,401	18,859		21,899
Other	11,790	6,434		6,839
Changes in operating assets and liabilities:
Accounts receivable	(27,742)	(38,548)		(23,858)
Inventory	(231,802)	(119,270)		(76,226)
Accounts payable	253,265	322,427		191,064
Income taxes payable	14,220	26,880		81,617
Accrued payroll	5,430	12,616		(19,341)
Accrued benefits and withholdings	3,042	(256)		18,904
Other	(9,844)	13,169	[1]	23,662	[1]
Net cash provided by operating activities	1,403,687	1,510,713	[1]	1,345,488	[1]
Investing activities:
Purchases of property and equipment	(465,940)	(476,344)		(414,020)
Proceeds from sale of property and equipment	4,464	5,119		2,758
Payments received on notes receivable	0	1,047		4,074
Other	(2,747)	(58,918)		0
Net cash used in investing activities	(464,223)	(529,096)		(407,188)
Financing activities:
Proceeds from borrowings on revolving credit facility	3,101,000	0		0
Payments on revolving credit facility	(2,755,000)	0		0
Proceeds from the issuance of long-term debt	748,800	499,160		0
Payment of debt issuance costs	(7,590)	(4,125)		0
Principal payments on capital leases	0	0		(25)
Repurchases of common stock	(2,172,530)	(1,505,437)		(1,136,213)
Net proceeds from issuance of common stock	45,762	59,634		64,613
Other	(156)	(552)	[1]	(934)	[1]
Net cash used in financing activities	(1,039,714)	(951,320)	[1]	(1,072,559)	[1]
Net (decrease) increase in cash and cash equivalents	(100,250)	30,297		(134,259)
Cash and cash equivalents at beginning of the year	146,598	116,301		250,560
Cash and cash equivalents at end of the year	46,348	146,598		116,301
Supplemental disclosures of cash flow information:
Income taxes paid	496,728	569,677		485,824
Interest paid, net of capitalized interest	$ 77,766	$ 63,648		$ 55,061

[1] Certain prior period amounts have been reclassified to conform to current period presentation. See Note 1 “Summary of Significant Accounting Policies” to the Consolidated Financial Statements for more information.