Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating Activities
Net income	$ 89,620	$ 67,265
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	7,915	6,792
Stock-based compensation	4,303	4,918
(Gain) loss on disposal of property, plant and equipment	(134)	10
Other non-cash adjustments	(233)	(308)
Changes in operating assets and liabilities:
Accounts receivable	(171,220)	(26,746)
Inventories	6,457	14,882
Prepaid expenses and other assets	(2,335)	210
Accounts payable	12,195	(3,777)
Accrued expenses and other liabilities	(591)	(16,548)
Income taxes receivable/payable	21,691	(3,640)
Net cash (used in) provided by operating activities	(32,332)	43,058
Investing Activities
Expenditures for property, plant and equipment	(62,613)	(19,061)
Proceeds from sales of property, plant and equipment	2,146
Net cash used in investing activities	(60,467)	(19,061)
Financing Activities
Borrowings under line of credit	173,000	89,500
Principal payments under line of credit	(173,000)	(89,500)
Repurchases of common stock	(44,124)	(24,172)
Proceeds from employee stock purchase and option plans	688	560
Financing costs	(361)
Net cash used in financing activities	(43,797)	(23,612)
Net (decrease) increase in cash and cash equivalents	(136,596)	385
Cash and cash equivalents, beginning of period	148,833	105,699
Cash and cash equivalents, end of period	12,237	106,084
Supplemental Disclosure:
Cash paid for interest	143	321
Cash paid for income taxes, net	$ 7,813	$ 23,371