Segment Information (Summary of Information by Business Segment) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Adjusted EBITDDA		$ 107,183	$ 135,386	$ 577,153	$ 218,330
Interest expense, net	[1]	(8,641)	(8,557)	(20,414)	(20,594)
Depreciation, depletion and amortization		(21,131)	(20,187)	(56,156)	(56,590)
Basis of real estate sold		6,697	5,249	22,733	14,440
Net gain on insurance recoveries		4,394		4,394
Pension settlement charge					(42,988)
Non-operating pension and other postretirement employee benefits		(3,271)	(3,557)	(9,956)	(10,670)
(Loss) gain on disposal of fixed assets		(1,139)	11	(1,700)	196
Income (loss) before income taxes		70,698	97,847	470,588	73,244
Bond discounts and deferred loan fees	[1]	403	407	1,209	1,219
Total depreciation, depletion and amortization		21,534	20,594	57,365	57,809
Operating Segments [Member]
Segment Reporting Information [Line Items]
Depreciation, depletion and amortization		21,131	20,187	56,156	56,590
Operating Segments [Member] | Timberlands [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDDA		76,023	59,649	221,140	120,290
Depreciation, depletion and amortization		11,893	13,821	33,792	37,978
Operating Segments [Member] | Wood Products [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDDA		26,566	81,644	356,654	105,780
Depreciation, depletion and amortization		8,879	5,983	21,261	17,411
Operating Segments [Member] | Real Estate Segment [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDDA		9,069	13,466	37,450	30,062
Depreciation, depletion and amortization		162	149	477	465
Basis of real estate sold		6,703	5,257	22,751	14,973
Corporate [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDDA		(11,496)	(15,361)	(35,028)	(34,567)
Depreciation, depletion and amortization		197	234	626	736
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDDA		7,021	(4,012)	(3,063)	(3,235)
Basis of real estate sold		$ (6)	$ (8)	$ (18)	$ (533)

[1] Bond discounts and deferred loan fees are reported within interest expense, net on the Condensed Consolidated Statements of Operations.