Condensed Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 34,782	$ 24,237
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	14,920	13,453
Stock-based compensation expense	5,277	5,844
Other non-cash items	3,203	1,624
Changes in assets and liabilities, net of acquisitions of businesses:
Accounts receivable, net	(36,920)	(37,520)
Inventories, net	(1,227)	(2,367)
Prepaid expenses and other assets	(687)	3,573
Accounts payable, trade	23,095	11,696
Accrued expenses and other liabilities	13,352	12,499
Net cash flows provided by operating activities	55,795	33,039
Cash flows from investing activities:
Capital expenditures	(17,912)	(17,545)
Acquisitions of businesses	(82,157)	(1,451)
Proceeds from note receivable	750	0
Proceeds from sales of fixed assets	1,999	70
Other investing activities	(49)	(48)
Net cash flows used for investing activities	(97,369)	(18,974)
Cash flows from financing activities:
Exercise of stock options and deferred stock units, net of shares tendered for payment	3,425	10,686
Proceeds from line of credit borrowings	182,315	135,452
Repayments under line of credit borrowings	(160,027)	(135,452)
Payment of special dividend	(46,706)	0
Payment of contingent consideration related to acquisitions	(3,513)	(2,813)
Other financing activities	(196)	0
Net cash flows (used for) provided by financing activities	(24,702)	7,873
Net (decrease) increase in cash	(66,276)	21,938
Cash and cash equivalents at beginning of period	66,280	9,939
Cash and cash equivalents at end of period	4	31,877
Cash paid during the period for:
Interest	204	159
Income taxes, net of refunds	$ 13,297	$ 8,358