Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating Activities
Net income	$ 67,265	$ 79,930
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	6,857	9,363
Stock-based compensation	4,918	3,645
Loss (gain) on disposal of property, plant and equipment	10	(29)
Other non-cash adjustments	(373)	(406)
Changes in operating assets and liabilities:
Accounts receivable	(26,746)	(104,250)
Inventories	14,882	(1,664)
Prepaid expenses and other assets	210	(2,616)
Accounts payable	(3,777)	14,863
Accrued expenses and other liabilities	(16,548)	(5,705)
Income taxes receivable/payable	(3,640)	5,195
Net cash provided by (used in) operating activities	43,058	(1,674)
Investing Activities
Expenditures for property, plant and equipment and intangibles	(19,061)	(17,697)
Proceeds from sales of property, plant and equipment		83
Net cash used in investing activities	(19,061)	(17,614)
Financing Activities
Borrowings under line of credit	89,500	167,750
Principal payments under line of credit	(89,500)	(159,250)
Repurchases of common stock	(24,172)	(17,230)
Proceeds from employee stock purchase and option plans	560	405
Net cash used in financing activities	(23,612)	(8,325)
Net increase (decrease) in cash and cash equivalents	385	(27,613)
Cash and cash equivalents, beginning of period	105,699	30,514
Cash and cash equivalents, end of period	106,084	2,901
Supplemental Disclosure:
Cash paid for interest	321	385
Cash paid for income taxes, net	$ 23,371	$ 19,618