Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 148,551	$ 132,884	$ 129,671
Adjustments to reconcile net income to cash flows provided by operating activities:
Depreciation and amortization	67,526	54,727	46,167
Stock-based compensation expense	14,065	20,036	15,420
Deferred taxes	13,874	6,808	(2,598)
Other non-cash items	(13)	4,371	1,540
Changes in assets and liabilities, net of acquisitions of businesses:
Accounts receivable, net	(11,352)	(12,601)	(13,899)
Inventories, net	(34,730)	(78,698)	(7,856)
Prepaid expenses and other assets	(17,691)	(10,898)	(15,553)
Accounts payable, trade	(17,335)	20,727	18,800
Accrued expenses and other liabilities	(6,287)	15,346	29,975
Net cash flows provided by operating activities	156,608	152,702	201,667
Cash flows from investing activities:
Capital expenditures	(119,827)	(87,221)	(44,671)
Acquisitions of businesses, net of cash acquired	(184,792)	(60,588)	(48,725)
Proceeds from note receivable	2,000	1,500	2,000
Other investing activities	(176)	434	(311)
Net cash flows used in investing activities	(302,795)	(145,875)	(91,707)
Cash flows from financing activities:
Exercise of stock-based awards, net of shares tendered for payment of taxes	(16,097)	(10,531)	2,574
Proceeds from line of credit borrowings	1,387,013	28,130	81,458
Repayments under line of credit borrowings	(1,146,953)	(28,130)	(81,458)
Proceeds from other borrowings	4,509	0	0
Payment of dividends	(59,270)	(51,057)	(34,437)
Payment of contingent consideration related to acquisitions	(3,068)	(5,301)	(3,204)
Repurchases of common stock	(28,695)	0	0
Other financing activities	(2,373)	(59)	(1,028)
Net cash flows provided by (used in) financing activities	135,066	(66,948)	(36,095)
Net (decrease) increase in cash and cash equivalents	(11,121)	(60,121)	73,865
Cash and cash equivalents at beginning of period	26,049	86,170	12,305
Cash and cash equivalents at end of period	14,928	26,049	86,170
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	5,645	1,650	1,992
Cash paid during the period for income taxes, net of refunds	39,991	53,620	65,792
Purchase of property and equipment in accrued expenses	$ 385	$ 2,640	$ 1,461