Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net income	$ 95,128	$ 67,847	$ 48,098
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	16,860	14,498	14,384
Deferred income taxes	194	5,433	1,024
Stock-based compensation	5,187	4,788	4,861
Loss (Gain) on disposal of property, plant and equipment	1,738	(185)	649
Excess tax benefits from stock compensation			(3,147)
Other non-cash adjustments	(406)	(284)	(271)
Changes in operating assets and liabilities:
Accounts receivable	(10,486)	(653)	(10,995)
Inventories	(3,635)	(5,442)	643
Prepaid expenses and other assets	(2,194)	(4,256)	905
Accounts payable	(4,804)	(6,966)	(2,317)
Accrued expenses and other liabilities	2,488	9,403	7,554
Income taxes receivable/payable	1,795	1,110	1,246
Net cash provided by operating activities	101,865	85,293	62,634
Investing Activities
Expenditures for property, plant and equipment	(15,040)	(14,551)	(23,333)
Proceeds from sales of property, plant and equipment	55	4,349	35
Acquisition of business, net of cash acquired	(71,804)		(31)
Net cash used in investing activities	(86,789)	(10,202)	(23,329)
Financing Activities
Financing costs		(485)	(3)
Borrowings under line of credit	201,000	242,700	225,500
Principal payments under line of credit	(201,000)	(249,700)	(218,500)
Repurchases of common stock	(3,617)	(55,216)	(53,313)
Proceeds from employee stock purchase and option plans	391	279	315
Excess tax benefits from stock compensation			3,147
Net cash used in financing activities	(3,226)	(62,422)	(42,854)
Net increase (decrease) in cash and cash equivalents	11,850	12,669	(3,549)
Cash and cash equivalents at beginning of year	18,664	5,995	9,544
Cash and cash equivalents at end of year	30,514	18,664	5,995
Supplemental disclosures of cash flow information:
Cash paid for interest	418	852	625
Cash paid for income taxes, net	$ 44,802	$ 28,626	$ 26,327