Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net earnings	$ 127,606	$ 111,931
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation of property and equipment	19,412	17,281
Gain on sale of property and equipment	(108)	(216)
Bad debt expense	2,883	2,796
Deferred income taxes	416	356
Stock-based compensation	1,620	1,380
Excess tax benefits from stock-based compensation	(451)	(550)
Amortization of non-compete agreements	132	132
Changes in operating assets and liabilities:
Trade accounts receivable	(66,065)	(61,646)
Inventories	(5,151)	(9,919)
Other current assets	18,140	7,031
Accounts payable	28,325	6,444
Accrued expenses	(5,059)	(10)
Income taxes	59,195	72,679
Other	(790)	(4,391)
Net cash provided by operating activities	180,105	143,298
Cash flows from investing activities:
Purchases of property and equipment	(43,922)	(32,564)
Proceeds from sale of property and equipment	1,663	1,054
Net increase in marketable securities	0	(2)
Net (increase) decrease in other assets	(23)	22
Net cash used in investing activities	(42,282)	(31,490)
Cash flows from financing activities:
Borrowings under line of credit	175,000	140,000
Payments against line of credit	(140,000)	(140,000)
Proceeds from exercise of stock options	2,080	1,641
Excess tax benefits from stock-based compensation	451	550
Purchases of common stock	(81,865)	(8,847)
Payments of dividends	(82,846)	(74,193)
Net cash used in financing activities	(127,180)	(80,849)
Effect of exchange rate changes on cash and cash equivalents	(4,349)	(444)
Net increase in cash and cash equivalents	6,294	30,515
Cash and cash equivalents at beginning of period	114,496	58,506
Cash and cash equivalents at end of period	120,790	89,021
Supplemental disclosure of cash flow information:
Cash paid during each period for interest	358	70
Net cash paid (received) during each period for income taxes	$ 16,292	$ (6,216)