Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating Activities
Net income	$ 109,401	$ 76,829
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,164	12,065
Stock-based compensation	5,045	3,913
Loss on disposal of property, plant and equipment	50	1,720
Other non-cash adjustments	(408)	(405)
Changes in operating assets and liabilities:
Accounts receivable	(21,034)	(14,407)
Inventories	(927)	4,860
Prepaid expenses and other assets	(3,155)	1,799
Accounts payable	8,245	1,203
Accrued expenses and other liabilities	619	(2,438)
Income taxes receivable/payable	4,369	7,698
Net cash provided by operating activities	115,369	92,837
Investing Activities
Expenditures for property, plant and equipment and intangibles	(21,611)	(11,108)
Proceeds from sales of property, plant and equipment	83
Acquisition of business		(71,523)
Net cash used in investing activities	(21,528)	(82,631)
Financing Activities
Borrowings under line of credit	172,250	201,000
Principal payments under line of credit	(172,250)	(201,000)
Repurchases of common stock	(17,723)	(3,617)
Proceeds from employee stock purchase and option plans	681	288
Net cash used in financing activities	(17,042)	(3,329)
Net increase in cash and cash equivalents	76,799	6,877
Cash and cash equivalents, beginning of period	30,514	18,664
Cash and cash equivalents, end of period	107,313	25,541
Supplemental Disclosure:
Cash paid for interest	662	416
Cash paid for income taxes, net	$ 39,170	$ 32,016