Condensed 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 income	$ 11,116	$ 9,387
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	6,381	4,890
Stock-based compensation expense	1,319	1,113
Other non-cash items	461	(109)
Changes in assets and liabilities, net of acquisitions of businesses:
Accounts receivable, net	(34,915)	(30,354)
Inventories	3,939	(6,679)
Prepaid expenses and other assets	(510)	(262)
Accounts payable	4,007	17,858
Accrued expenses and other liabilities	11,362	7,239
Net cash flows provided by operating activities	3,160	3,083
Cash flows from investing activities:
Capital expenditures	(5,684)	(3,136)
Acquisitions of businesses	(1,164)	(7,250)
Proceeds from maturity of short-term investments		5,000
Other investing activities	25	(48)
Net cash flows used for investing activities	(6,823)	(5,434)
Cash flows from financing activities:
Exercise of stock options and deferred stock units	974	339
Proceeds from line of credit borrowings	37,702
Repayments under line of credit borrowings	(37,702)
Payment of contingent consideration	(354)	(3)
Other financing activities		(137)
Net cash flows provided by financing activities	620	199
Net decrease in cash	(3,043)	(2,152)
Cash and cash equivalents at beginning of period	6,584	38,880
Cash and cash equivalents at end of period	3,541	36,728
Supplemental disclosure of cash flow information:
Interest	96	71
Income taxes, net of refunds	$ (9)	$ 79