Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities
Net income	$ 81,972	$ 71,993	$ 57,638
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	11,592	9,746	8,980
Amortization	1,284	1,559	2,348
Share-based compensation	8,465	8,233	7,790
Excess tax benefits from share-based compensation	(4,487)	(3,118)	(1,877)
Provision for doubtful accounts receivable, net of write-offs	(422)	(1,202)	(4,324)
Provision for inventory obsolescence, net	447	(11)	(721)
Change in deferred income taxes	3,168	2,605	1,795
Loss on sale of property and equipment	44	263	324
Equity earnings in unconsolidated investments	(316)	(209)	(105)
(Gains) losses on foreign currency transactions	(111)	592	(1,498)
Goodwill impairment	6,946	1,550	0
Other	138	195	145
Changes in operating assets and liabilities, net of effects of acquisitions:
Receivables	(3,396)	(5,887)	4,832
Product inventories	(9,232)	(35,339)	15,951
Prepaid expenses and other assets	(1,159)	(2,951)	4,694
Accounts payable	20,253	6,402	(14,417)
Accrued expenses and other current liabilities	3,892	20,682	12,404
Net cash provided by operating activities	119,078	75,103	93,959
Investing activities
Acquisition of businesses, net of cash acquired	(4,699)	(5,934)	(6,173)
Purchases of property and equipment, net of sale proceeds	(16,271)	(19,454)	(8,078)
Other investments, net	(238)	(190)	0
Net cash used in investing activities	(21,208)	(25,578)	(14,251)
Financing activities
Proceeds from revolving line of credit	607,923	749,349	453,039
Payments on revolving line of credit	(524,341)	(700,749)	(457,568)
Payments on long-term debt and other long-term liabilities	(100,022)	(149)	(48,225)
Payments of deferred acquisition consideration	0	(500)	(1,000)
Payments of deferred financing costs	0	(1,674)	(145)
Excess tax benefits from share-based compensation	4,487	3,118	1,877
Proceeds from stock issued under share-based compensation plans	20,205	13,085	6,293
Payments of cash dividends	(29,135)	(26,470)	(25,746)
Purchases of treasury stock	(81,761)	(76,564)	(13,683)
Net cash used in financing activities	(102,644)	(40,554)	(85,158)
Effect of exchange rate changes on cash and cash equivalents	(250)	(1,205)	(672)
Change in cash and cash equivalents	(5,024)	7,766	(6,122)
Cash and cash equivalents at beginning of year	17,487	9,721	15,843
Cash and cash equivalents at end of year	$ 12,463	$ 17,487	$ 9,721