Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 132,884	$ 129,671	$ 74,345
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	54,727	46,167	41,624
Stock-based compensation expense	20,036	15,420	14,043
Deferred taxes	6,808	(2,598)	1,062
Other non-cash items	4,371	1,540	1,335
Changes in assets and liabilities, net of acquisitions of businesses:
Accounts receivable, net	(12,601)	(13,899)	2,082
Inventories, net	(78,698)	(7,856)	(31,276)
Prepaid expenses and other assets	(10,898)	(15,553)	(2,249)
Accounts payable, trade	20,727	18,800	(21,783)
Accrued expenses and other liabilities	17,727	31,715	15,835
Net cash flows provided by operating activities	155,083	203,407	95,018
Cash flows from investing activities:
Capital expenditures	(87,221)	(44,671)	(28,989)
Acquisitions of businesses, net of cash acquired	(60,588)	(48,725)	(41,058)
Proceeds from note receivable	1,500	2,000	2,000
Proceeds from sales of fixed assets	467	698	2,337
Other investing activities	(33)	(1,009)	(406)
Net cash flows used for investing activities	(145,875)	(91,707)	(66,116)
Cash flows from financing activities:
Exercise of stock-based awards, net of shares tendered for payment of taxes	(10,531)	2,574	1,470
Proceeds from line of credit borrowings	28,130	81,458	614,629
Repayments under line of credit borrowings	(28,130)	(81,458)	(630,279)
Payment of dividends	51,057	34,437	48,227
Proceeds from shelf-loan borrowing	0	0	50,000
Payment of contingent consideration related to acquisitions	(7,682)	(4,944)	(3,974)
Other financing activities	(59)	(1,028)	(220)
Net cash flows used for financing activities	(69,329)	(37,835)	(16,601)
Net (decrease) increase in cash and cash equivalents	(60,121)	73,865	12,301
Cash and cash equivalents at beginning of period	86,170	12,305	4
Cash and cash equivalents at end of period	26,049	86,170	12,305
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	1,650	1,992	2,113
Cash paid during the period for income taxes, net of refunds	53,620	65,792	33,782
Capital Expenditures Incurred but Not yet Paid	$ 2,640	$ 1,461	$ 646