Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income		$ 44,262	$ 121,081
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization		52,589	53,685
Basis of real estate sold		14,211	10,673
Gain on sale of facility		(9,176)
Loss on extinguishment of debt		5,512
Change in deferred taxes		(16,943)	13,879
Pension and other postretirement employee benefits		8,907	12,221
Equity-based compensation expense		5,362	6,518
Other, net		(2,692)	(1,220)
Change in working capital and operating-related activities, net		13,745	(9,429)
Real estate development expenditures		(5,738)	(3,081)
Funding of pension and other postretirement employee benefits		(4,612)	(55,959)
Net cash provided by operating activities		105,427	148,368
CASH FLOWS FROM INVESTING ACTIVITIES
Property, plant and equipment additions		(25,596)	(18,496)
Timberlands reforestation and roads		(13,269)	(12,464)
Acquisition of timber and timberlands		(278)	(166)
Proceeds on sale of facility		58,793
Proceeds on disposition of property, plant and equipment		2,017	11
Other, net		520	644
Cash and cash equivalents acquired in Deltic merger			3,419
Net cash provided by (used in) investing activities		22,187	(27,052)
CASH FLOWS FROM FINANCING ACTIVITIES
Dividends to common stockholders		(80,834)	(75,305)
Proceeds from Potlatch revolving line of credit			100,000
Repayment of revolving line of credit			(100,000)
Proceeds from issue of long-term debt		150,000	100,000
Repayment of long-term debt		(150,000)	(14,250)
Premiums and fees on debt retirement		(4,865)
Repurchase of common stock		(25,173)
Other, net		(393)	(4,975)
Net cash used in financing activities		(111,265)	(100,530)
Change in cash, cash equivalents and restricted cash		16,349	20,786
Cash, cash equivalents and restricted cash at beginning of period		79,441	120,457
Cash, cash equivalents and restricted cash at end of period		95,790	141,243
NONCASH INVESTING AND FINANCING ACTIVITIES
Long-term debt assumed by buyer in sale of facility		29,000
Accrued property, plant and equipment additions		453	785
Accrued timberlands reforestation and roads		1,406	1,034
Earnings and profits distribution payable			222,000
Cash and cash equivalents		94,747	137,535
Restricted cash included in other short-term and long-term assets	[1]	$ 1,043	$ 3,708
Restricted Cash, Asset, Statement of Financial Position [Extensible List]		us-gaap:OtherAssetsMember	us-gaap:OtherAssetsMember
Deltic [Member]
CASH FLOWS FROM FINANCING ACTIVITIES
Repayment of revolving line of credit			$ (106,000)
NONCASH INVESTING AND FINANCING ACTIVITIES
Equity issued as consideration for our merger with Deltic			$ 1,142,775

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