Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net (loss) income		$ (16,832)	$ 6,560
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation, depletion and amortization		19,044	16,274
Basis of real estate sold		6,498	1,556
Gain on sale of facility			(9,176)
Loss on extinguishment of debt			5,512
Change in deferred taxes		(12,383)	(16,099)
Pension and other postretirement employee benefits		6,068	3,106
Pension settlement charge		42,988
Equity-based compensation expense		1,885	1,617
Other, net		237	(786)
Change in working capital and operating-related activities, net		2,557	13,983
Real estate development expenditures		(378)	(1,766)
Funding of pension and other postretirement employee benefits		(1,546)	(1,714)
Net cash provided by operating activities		48,138	19,067
CASH FLOWS FROM INVESTING ACTIVITIES
Property, plant and equipment additions		(5,039)	(3,760)
Timberlands reforestation and roads		(4,310)	(4,242)
Acquisition of timber and timberlands		(4,190)
Proceeds on sale of facility		1,000	60,045
Other, net		1,505	130
Net cash (used in) provided by investing activities		(11,034)	52,173
CASH FLOWS FROM FINANCING ACTIVITIES
Distributions to common stockholders		(26,941)	(27,065)
Repurchase of common stock		(12,355)	(10,158)
Proceeds from issue of long-term debt			150,000
Repayment of long-term debt			(150,000)
Premiums and fees on debt retirement			(4,865)
Other, net		(242)	(213)
Net cash used in financing activities		(39,538)	(42,301)
Change in cash, cash equivalents and restricted cash		(2,434)	28,939
Cash, cash equivalents and restricted cash at beginning of period		84,254	79,441
Cash, cash equivalents and restricted cash at end of period		81,820	108,380
NONCASH INVESTING AND FINANCING ACTIVITIES
Long-term debt assumed by buyer in sale of facility			29,000
Accrued property, plant and equipment additions		1,380	2,590
Accrued timberlands reforestation and roads		260	17
Cash and cash equivalents		79,484	104,787
Restricted cash included in other short-term and long-term assets	[1]	$ 2,336	$ 3,593
Restricted Cash, Asset, Statement of Financial Position [Extensible List]		us-gaap:OtherAssetsMember	us-gaap:OtherAssetsMember

[1] Amounts included in restricted cash represent proceeds held by a qualified intermediary that are intended to be reinvested in timber and timberlands.