Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income	$ 94,560	$ 83,282
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	32,476	25,530
Stock-based compensation expense	9,762	9,312
Other non-cash items	(927)	2,198
Changes in assets and liabilities, net of acquisitions of businesses:
Accounts receivable, net	(52,236)	(61,455)
Inventories, net	(14,556)	(6,804)
Prepaid expenses and other assets	(5,743)	(9,337)
Accounts payable, trade	5,412	22,542
Accrued expenses and other liabilities	10,181	31,431
Net cash flows provided by operating activities	78,929	96,699
Cash flows from investing activities:
Capital expenditures	(54,539)	(43,276)
Acquisitions of businesses, net of cash acquired	(153,415)	(67,876)
Proceeds from note receivable	2,000	0
Other investing activities	(1,016)	257
Net cash flows used in investing activities	(206,970)	(110,895)
Cash flows from financing activities:
Exercise of stock-based awards, net of shares tendered for payment of taxes	(14,114)	(7,543)
Proceeds from line of credit borrowings	631,148	0
Repayments under line of credit borrowings	(469,148)	0
Proceeds from other borrowings	4,509	0
Payment of dividends	28,985	24,887
Payment of contingent consideration related to acquisitions	(3,011)	(1,524)
Other financing activities	(556)	(59)
Net cash flows provided by (used in) financing activities	119,843	(34,013)
Net decrease in cash and cash equivalents	(8,198)	(48,209)
Cash and cash equivalents at beginning of period	26,049	86,170
Cash and cash equivalents at end of period	17,851	37,961
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	2,582	941
Cash paid during the period for income taxes, net of refunds	24,907	17,620
Purchase of property and equipment in accrued expenses	$ 664	$ 2,072