Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019		Mar. 31, 2018
Operating activities:
Net income	$ 321,152		$ 304,906
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and intangibles	63,964		69,920
Amortization of debt discount and issuance costs	918		795
Deferred income taxes	4,312		4,370
Share-based compensation programs	5,424		5,176
Other	2,245		2,244
Changes in operating assets and liabilities:
Accounts receivable	(60,914)		(10,421)
Inventory	(35,405)		(42,643)
Accounts payable	60,918		32,756
Income taxes payable	82,476		79,380
Other	(4,468)		(14,206)
Net cash provided by operating activities	440,622		432,277
Investing activities:
Purchases of property and equipment	(152,914)		(114,843)
Proceeds from sale of property and equipment	1,811		752
Other	(295)		(375)
Net cash used in investing activities	(151,398)		(114,466)
Financing activities:
Proceeds from borrowings on revolving credit facility	874,000		755,000
Payments on revolving credit facility	(831,000)		(541,000)
Repurchases of common stock	(321,856)		(549,450)
Net proceeds from issuance of common stock	15,224		11,972
Other	(190)		(2,156)
Net cash used in financing activities	(263,822)		(325,634)
Net increase (decrease) in cash and cash equivalents	25,402		(7,823)
Cash and cash equivalents at beginning of the period	31,315	[1]	46,348
Cash and cash equivalents at end of the period	56,717		38,525
Supplemental disclosures of cash flow information:
Income taxes paid	5,335		7,939
Interest paid, net of capitalized interest	$ 47,796		$ 48,763

[1] The balance sheet at December 31, 2018, 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.