Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)		$ 131,106	$ (16,832)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization		18,399	19,044
Basis of real estate sold		8,823	6,498
Change in deferred taxes		1,490	(12,383)
Pension and other postretirement employee benefits		5,627	6,068
Pension settlement charge			42,988
Equity-based compensation expense		1,930	1,885
Other, net		(387)	237
Change in working capital and operating-related activities, net		6,713	2,557
Real estate development expenditures		(2,315)	(378)
Funding of pension and other postretirement employee benefits		(1,421)	(1,546)
Net cash provided by operating activities		169,965	48,138
CASH FLOWS FROM INVESTING ACTIVITIES
Property, plant and equipment additions		(7,762)	(5,039)
Timberlands reforestation and roads		(3,956)	(4,310)
Acquisition of timber and timberlands			(4,190)
Proceeds on sale of facility			1,000
Other, net		189	1,505
Net cash used in investing activities		(11,529)	(11,034)
CASH FLOWS FROM FINANCING ACTIVITIES
Distributions to common stockholders		(27,484)	(26,941)
Repurchase of common stock			(12,355)
Other, net		(591)	(242)
Net cash used in financing activities		(28,075)	(39,538)
Change in cash, cash equivalents and restricted cash		130,361	(2,434)
Cash, cash equivalents and restricted cash at beginning of period		252,340	84,254
Cash, cash equivalents and restricted cash at end of period		382,701	81,820
NONCASH INVESTING AND FINANCING ACTIVITIES
Accrued property, plant and equipment additions		2,263	1,380
Accrued timberlands reforestation and roads		813	260
Cash and cash equivalents		382,032	79,484
Restricted cash included in other long-term assets	[1]	$ 669	$ 2,336
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.