Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net earnings	$ 100,194	$ 79,547
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation of property and equipment	12,415	10,481
Loss on sale of property and equipment	174	25
Bad debt expense	2,329	2,267
Deferred income taxes	1,863	(56)
Stock based compensation	1,050	900
Amortization of non-compete agreements	148	148
Changes in operating assets and liabilities:
Trade accounts receivable	(50,617)	(57,819)
Inventories	(1,734)	(19,082)
Other current assets	15,536	8,757
Accounts payable	2,334	8,045
Accrued expenses	1,134	(3,934)
Income taxes	44,941	43,220
Other	2,421	1,785
Net cash provided by operating activities	132,188	74,284
Cash flows from investing activities:
Purchase of property and equipment	(28,212)	(21,206)
Proceeds from sale of property and equipment	985	621
Net (increase) decrease in marketable securities	(29)	463
(Increase) decrease in other assets	(57)	220
Net cash used in investing activities	(27,313)	(19,902)
Cash flows from financing activities:
Proceeds from exercise of stock options	18,285	0
Tax benefits from exercise of stock options	7,697	0
Payment of dividends	(50,197)	(73,715)
Net cash used in financing activities	(24,215)	(73,715)
Effect of exchange rate changes on cash	542	488
Net increase (decrease) in cash and cash equivalents	81,202	(18,845)
Cash and cash equivalents at beginning of period	117,676	143,693
Cash and cash equivalents at end of period	198,878	124,848
Supplemental disclosure of cash flow information:
Cash paid during each period for income taxes	$ 21,828	$ 6,100