Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities
Net income	$ 8,927	$ 8,678
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	2,929	2,738
Deferred income taxes	279	(490)
Share-based compensation	1,191	1,028
Equity method investment earnings	0	(471)
Changes in Operating Assets and Liabilities:
Receivables, net	(185)	(10,302)
Inventory	(5,727)	(1,130)
Prepaid expenses	(1,005)	(742)
Accounts payable	(2,238)	(943)
Accounts payable to affiliate, net	0	(542)
Accrued expenses	(4,009)	(1,627)
Income taxes payable	1,048	3,239
Deferred credit	(217)	(201)
Accrued retirement health and life insurance benefits	(114)	(177)
Net cash provided by (used in) operating activities	879	(942)
Cash Flows from Investing Activities
Additions to plant, property and equipment	(6,978)	(6,454)
Other, net	(62)	0
Net cash used in investing activities	(7,040)	(6,454)
Cash Flows from Financing Activities
Purchase of treasury stock for tax withholding on share-based compensation	(2,073)	(1,131)
Payment of dividends and dividend equivalents	(1,375)	(688)
Principal payments on long-term debt	(93)	(89)
Proceeds from credit agreement	7,741	10,500
Payments on credit agreement	0	(2,765)
Net cash provided by financing activities	4,200	5,827
Decrease in cash and cash equivalents	(1,961)	(1,569)
Cash and cash equivalents, beginning of period	3,084	1,569
Cash and cash equivalents, end of period	$ 1,123	$ 0