Statements of Cash Flow - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating Activities:
Net income	$ 30,955	$ 31,193
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	9,321	8,785
Deferred income taxes	3,327	816
Stock-based compensation attributable to equity awards	1,091	1,262
Other	520	(111)
Changes in operating assets and liabilities:
Accounts receivable	30,331	(20,615)
Inventories	1,804	6,328
Other assets	(1,652)	(200)
Trade accounts payable and accrued liabilities	(21,514)	2,266
Current income taxes receivable / payable	6,101	(1,873)
Net cash provided by operating activities	60,284	27,851
Investing Activities:
Purchases of property, plant and equipment	(21,921)	(21,210)
Proceeds from sale of assets	90	22
Net cash used in investing activities	(21,831)	(21,188)
Financing Activities:
Purchase of treasury stock	(20,662)	0
Proceeds from issuance of common stock, net	2,455	568
Dividends paid	(828)	(836)
Net cash used in financing activities	(19,035)	(268)
Net increase in cash and cash equivalents	19,418	6,395
Cash and cash equivalents at beginning of period	230,965	178,405
Cash and cash equivalents at end of period	$ 250,383	$ 184,800