Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 144,738	$ 134,572	$ 95,128
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,031	16,597	16,860
Deferred income taxes	7,706	1,037	194
Stock-based compensation	6,930	6,344	5,187
Loss on disposal of property, plant and equipment	285	47	1,738
Other non-cash adjustments	(218)	(406)	(406)
Changes in operating assets and liabilities:
Accounts receivable	12,701	(24,281)	(10,486)
Inventories	1,695	(23,276)	(3,635)
Prepaid expenses and other assets	(1,652)	(613)	(2,194)
Accounts payable	(16,666)	21,131	(4,804)
Accrued expenses and other liabilities	(10,823)	5,040	2,488
Income taxes receivable/payable	(2,375)	1,929	1,795
Net cash provided by operating activities	156,352	138,121	101,865
Investing Activities
Expenditures for property, plant and equipment and intangibles	(67,265)	(33,816)	(15,040)
Proceeds from sales of property, plant and equipment	21	83	55
Acquisition of business, net of cash acquired			(71,804)
Net cash used in investing activities	(67,244)	(33,733)	(86,789)
Financing Activities
Borrowings under line of credit	89,500	172,250	201,000
Principal payments under line of credit	(89,500)	(172,250)	(201,000)
Repurchases of common stock	(46,545)	(30,085)	(3,617)
Proceeds from employee stock purchase and option plans	1,089	882	391
Financing costs	(518)
Net cash used in financing activities	(45,974)	(29,203)	(3,226)
Net increase in cash and cash equivalents	43,134	75,185	11,850
Cash and cash equivalents, beginning of period	105,699	30,514	18,664
Cash and cash equivalents, end of period	148,833	105,699	30,514
Supplemental Disclosure:
Cash paid for interest	321	662	418
Cash paid for income taxes, net	$ 39,612	$ 48,238	$ 44,802