Merger with Deltic (Narrative) (Details) $ in Thousands, shares in Millions					1 Months Ended	3 Months Ended								10 Months Ended	12 Months Ended
		Nov. 15, 2018 shares	Feb. 20, 2018 USD ($) a Sawmill	Feb. 19, 2018 USD ($)	Feb. 28, 2018 shares	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Total assets acquired			$ 1,467,535
Liabilities assumed			$ 324,760
Merger-related costs	[1]															$ 22,119	$ 3,409
Revenue						$ 203,499	$ 226,302	$ 215,581	$ 181,716	$ 217,250	$ 289,199	$ 268,233	$ 199,897		$ 827,098	974,579	678,595
Income before taxes															$ 56,671	142,079	118,474
Deltic [Member]
Business Acquisition [Line Items]
Acres of timberland | a			530,000
Number of sawmills | Sawmill			2
Area of diversified timberland base after merger | a			1,900,000
Number of share exchanged under agreement			180.00%
Total assets acquired			$ 1,400,000
Equity consideration transferred			1,100,000
Liabilities assumed			$ 300,000
Merger-related costs																22,100	3,400
Merger related costs, professional fees																12,200	3,300
Restructuring costs, termination benefits																9,900	100
Revenue														$ 265,500
Income before taxes														$ 21,600
Non-recurring merger-related costs				$ 18,900												$ 27,600	$ 16,800
Number of shares issued upon merger | shares					22.0
Deltic [Member] | Special Distribution [Member]
Business Acquisition [Line Items]
Number of shares issued upon merger | shares		4.8
Business combination, estimated shares settle in non cash amount of liability | shares															4.8
Deltic [Member] | Arkansas [Member]
Business Acquisition [Line Items]
Area of diversified timberland base after merger | a			930,000

[1] For integration and restructuring costs related to the merger with Deltic see Note 2: Merger with Deltic.