Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net earnings	$ 109,048	$ 100,194
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation of property and equipment	15,152	12,415
(Gain) loss on sale of property and equipment	(213)	174
Bad debt expense	2,045	2,329
Deferred income taxes	379	1,863
Stock based compensation	1,350	1,050
Excess tax benefits from stock based compensation	(954)	0
Amortization of non-compete agreements	26	148
Changes in operating assets and liabilities:
Trade accounts receivable	(48,619)	(50,617)
Inventories	14,899	(1,734)
Other current assets	13,478	15,536
Accounts payable	(2,692)	2,334
Accrued expenses	(64)	1,134
Income taxes	60,001	44,941
Other	(3,592)	2,421
Net cash provided by operating activities	160,244	132,188
Cash flows from investing activities:
Purchase of property and equipment	(55,513)	(28,212)
Proceeds from sale of property and equipment	1,267	985
Net increase in marketable securities	(63)	(29)
Increase in other assets	(3)	(57)
Net cash used in investing activities	(54,312)	(27,313)
Cash flows from financing activities:
Proceeds from Unsecured Lines of Credit	20,000
Borrowings under line of credit		0
Payments against line of credit	(20,000)	0
Proceeds from exercise of stock options	2,821	18,285
Excess tax benefits from stock based compensation	954	7,697
Payment of dividends	(29,662)	(50,197)
Net cash used in financing activities	(25,887)	(24,215)
Effect of exchange rate changes on cash	(416)	542
Net increase in cash and cash equivalents	79,629	81,202
Cash and cash equivalents at beginning of period	79,611	117,676
Cash and cash equivalents at end of period	159,240	198,878
Supplemental disclosure of cash flow information:
Cash paid during each period for interest	34	0
Cash paid during each period for income taxes	$ 6,502	$ 21,828