Condensed Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues		$ 289,199	$ 190,441	$ 757,329	$ 503,351
Costs and expenses:
Cost of goods sold		195,584	124,727	515,645	348,581
Selling, general and administrative expenses		14,901	13,240	45,449	37,687
Deltic merger-related costs	[1]	972	27	21,245	27
Environmental charges for Avery Landing			4,978		4,978
Loss (gain) on lumber price swap			2,080		(1,185)
Total costs and expenses		211,457	145,052	582,339	390,088
Operating income		77,742	45,389	174,990	113,263
Interest expense, net		(10,109)	(7,336)	(25,125)	(19,654)
Non-operating pension and other postretirement employee benefit costs		(1,942)	(1,596)	(5,707)	(4,788)
Income before income taxes		65,691	36,457	144,158	88,821
Income taxes		(5,355)	(2,757)	(23,077)	(13,956)
Net income		$ 60,336	$ 33,700	$ 121,081	$ 74,865
Net income per share:
Basic (in dollars per share)		$ 0.96	$ 0.83	$ 2.06	$ 1.83
Diluted (in dollars per share)		0.93	0.82	2.03	1.82
Dividends per share (in dollars per share)		$ 0.40	$ 0.375	$ 1.20	$ 1.125
Weighted-average shares outstanding (in thousands):
Basic (in shares)		62,985,517	40,829,399	58,765,381	40,814,135
Diluted (in shares)		64,721,657	41,250,457	59,542,200	41,182,795

[1] For integration and restructuring costs related to the merger with Deltic see Note 13: Merger, Integration and Other Costs.