Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 83,282	$ 73,528
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	25,530	22,190
Stock-based compensation expense	9,312	7,274
Other non-cash items	2,198	809
Changes in assets and liabilities, net of acquisitions of businesses:
Accounts receivable, net	(61,455)	(58,777)
Inventories, net	(6,804)	25,590
Prepaid expenses and other assets	(9,337)	(4,199)
Accounts payable, trade	22,542	21,496
Accrued expenses and other liabilities	32,476	45,440
Net cash flows provided by operating activities	97,744	133,351
Cash flows from investing activities:
Capital expenditures	(43,276)	(13,309)
Acquisitions of businesses, net of cash acquired	(67,876)	(34,237)
Proceeds from sales of fixed assets	265	337
Other investing activities	(8)	(237)
Net cash flows used for investing activities	(110,895)	(47,446)
Cash flows from financing activities:
Exercise of stock-based awards, net of shares tendered for payment of taxes	(7,543)	(1,144)
Proceeds from line of credit borrowings	0	81,458
Repayments under line of credit borrowings	0	(81,458)
Payment of dividends	24,887	14,707
Payment of contingent consideration related to acquisitions	(2,569)	(2,715)
Other financing activities	(59)	(1,084)
Net cash flows used for financing activities	(35,058)	(19,650)
Net (decrease) increase in cash and cash equivalents	(48,209)	66,255
Cash and cash equivalents at beginning of period	86,170	12,305
Cash and cash equivalents at end of period	37,961	78,560
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	941	1,082
Cash paid during the period for income taxes, net of refunds	17,620	19,134
Purchase of property and equipment in accrued expenses	$ 2,072	$ 308