Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:
Net earnings	$ 375,759	$ 349,407
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation of property and equipment	53,476	47,212
Gain on sale of property and equipment	(722)	(568)
Bad debt expense	8,429	7,087
Deferred income taxes	1,414	519
Stock-based compensation	4,620	4,050
Excess tax benefits from stock-based compensation	(1,925)	(2,682)
Amortization of non-compete agreements	395	290
Changes in operating assets and liabilities:
Trade accounts receivable	(116,363)	(88,580)
Inventories	(52,311)	(40,602)
Other current assets	(19,346)	(23,386)
Accounts payable	21,326	27,112
Accrued expenses	33,564	26,292
Income taxes	34,975	12,044
Other	(10,349)	(2,922)
Net cash provided by operating activities	332,942	315,273
Cash flows from investing activities:
Purchases of property and equipment	(143,547)	(145,559)
Proceeds from sale of property and equipment	4,154	4,291
Net decrease (increase) in marketable securities	451	(87)
Net increase in other assets	(23)	(79)
Net cash used in investing activities	(138,965)	(141,434)
Cash flows from financing activities:
Borrowings under line of credit	540,000	100,000
Payments against line of credit	(435,000)	(100,000)
Proceeds from exercise of stock options	7,036	9,039
Excess tax benefits from stock-based compensation	1,925	2,682
Purchases of common stock	(26,697)	(9,080)
Payments of dividends	(222,546)	(163,219)
Net cash used in financing activities	(135,282)	(160,578)
Effect of exchange rate changes on cash	(872)	(682)
Net increase in cash and cash equivalents	57,823	12,579
Cash and cash equivalents at beginning of period	58,506	79,611
Cash and cash equivalents at end of period	116,329	92,190
Supplemental disclosure of cash flow information:
Cash paid during each period for interest	591	61
Net cash paid during each period for income taxes	$ 175,453	$ 192,408