Statements of Cash Flow - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities:
Net income	$ 18,607	$ 13,411
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,571	4,344
Deferred income taxes	2,719	48
Stock-based compensation attributable to equity awards	460	760
Other	530	(49)
Changes in operating assets and liabilities:
Accounts receivable	(1,725)	3,883
Inventories	(884)	775
Other assets	(2,127)	724
Trade accounts payable and accrued liabilities	(16,302)	(16,437)
Current income taxes receivable / payable	3,156	3,947
Net cash provided by operating activities	9,005	11,406
Investing Activities:
Purchases of property, plant and equipment	(12,224)	(11,872)
Proceeds from sale of assets	90	22
Net cash used in investing activities	(12,134)	(11,850)
Financing Activities:
Purchase of treasury stock	(20,580)	0
Proceeds from issuance of common stock, net	0	431
Dividends paid	(418)	(418)
Net cash provided by (used in) financing activities	(20,998)	13
Net decrease in cash and cash equivalents	(24,127)	(431)
Cash and cash equivalents at beginning of period	230,965	178,405
Cash and cash equivalents at end of period	$ 206,838	$ 177,974