Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Operating activities
Net income	$ 78,051	$ 69,973
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	7,021	6,338
Amortization	696	622
Share-based compensation	4,657	4,111
Excess tax benefits from share-based compensation	(3,920)	(3,187)
Equity earnings in unconsolidated investments	(133)	(55)
Other	(73)	(1,633)
Changes in operating assets and liabilities, net of effects of acquisitions:
Receivables	(180,075)	(165,713)
Product inventories	(21,936)	(24,134)
Prepaid expenses and other assets	(1,350)	459
Accounts payable	18,065	39,458
Accrued expenses and other current liabilities	48,109	40,783
Net cash used in operating activities	(50,888)	(32,978)
Investing activities
Acquisition of businesses, net of cash acquired	(4,612)	(1,188)
Purchase of property and equipment, net of sale proceeds	(11,921)	(10,500)
Other investments, net	96	29
Net cash used in investing activities	(16,437)	(11,659)
Financing activities
Proceeds from revolving line of credit	457,218	399,472
Payments on revolving line of credit	(380,665)	(329,928)
Proceeds from asset-backed financing	121,600	0
Payments on asset-backed financing	(13,600)	0
Payments on long-term debt and other long-term liabilities	0	(10)
Excess tax benefits from share-based compensation	3,920	3,187
Proceeds from stock issued under share-based compensation plans	6,335	13,489
Payments of cash dividends	(18,410)	(16,308)
Purchases of treasury stock	(88,745)	(10,437)
Net cash provided by financing activities	87,653	59,465
Effect of exchange rate changes on cash and cash equivalents	(771)	(355)
Change in cash and cash equivalents	19,557	14,473
Cash and cash equivalents at beginning of period	8,006	12,463
Cash and cash equivalents at end of period	$ 27,563	$ 26,936