Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating activities
Net income	$ 89,969	$ 82,108
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	8,481	7,071
Amortization	962	1,243
Share-based compensation	6,236	6,143
Excess tax benefits from share-based compensation	(2,534)	(2,229)
Equity earnings in unconsolidated investments	(187)	(185)
Goodwill impairment	6,946	0
Other	278	(3,892)
Changes in operating assets and liabilities, net of effects of acquisitions:
Receivables	(63,015)	(55,941)
Product inventories	39,644	10,999
Prepaid expenses and other assets	2,607	677
Accounts payable	(15,500)	(49,542)
Accrued expenses and other current liabilities	50,643	35,522
Net cash provided by operating activities	124,530	31,974
Investing activities
Acquisition of businesses, net of cash acquired	(4,580)	(2,961)
Purchase of property and equipment, net of sale proceeds	(13,717)	(16,959)
Other investments, net	(249)	(177)
Net cash used in investing activities	(18,546)	(20,097)
Financing activities
Proceeds from revolving line of credit	482,669	446,649
Payments on revolving line of credit	(415,641)	(376,649)
Payments on long-term debt and other long-term liabilities	(100,017)	(145)
Payments of deferred acquisition consideration	0	(500)
Excess tax benefits from share-based compensation	2,534	2,229
Proceeds from stock issued under share-based compensation plans	13,180	9,506
Payments of cash dividends	(21,669)	(19,798)
Purchases of treasury stock	(55,088)	(62,842)
Net cash used in financing activities	(94,032)	(1,550)
Effect of exchange rate changes on cash and cash equivalents	(621)	608
Change in cash and cash equivalents	11,331	10,935
Cash and cash equivalents at beginning of period	17,487	9,721
Cash and cash equivalents at end of period	$ 28,818	$ 20,656