Merger with Deltic (Summary of Fair Value Measurements of Assets Acquired and Liabilities Assumed) (Details) $ in Thousands	Feb. 20, 2018 USD ($)
ASSETS
Cash and cash equivalents	$ 3,419
Customer receivables, net	12,709
Inventories	17,316
Other current assets	8,800
Real estate held for development and sale	77,000
Property, plant and equipment	260,769
Timber and timberlands	1,060,913
Mineral rights	6,236
Trade name and customer relationships intangibles	19,500
Other long-term assets	3,556
Total assets acquired	1,470,218
LIABILITIES
Accounts payable and accrued liabilities	16,022
Current portion of pension and other postretirement employee benefits	754
Long-term debt	229,968
Pension and other postretirement employee benefits	36,155
Deferred tax liabilities, net	43,608
Other long-term liabilities	936
Total liabilities assumed	327,443
Net assets acquired	1,142,775
Previously Reported [Member]
ASSETS
Cash and cash equivalents	3,419
Customer receivables, net	12,709
Inventories	17,316
Other current assets	8,276
Real estate held for development and sale	79,000
Property, plant and equipment	265,901
Timber and timberlands	1,060,000
Trade name and customer relationships intangibles	19,000
Other long-term assets	2,010
Total assets acquired	1,467,631
LIABILITIES
Accounts payable and accrued liabilities	12,604
Current portion of pension and other postretirement employee benefits	754
Long-term debt	229,968
Pension and other postretirement employee benefits	36,155
Deferred tax liabilities, net	44,439
Other long-term liabilities	936
Total liabilities assumed	324,856
Net assets acquired	1,142,775
Measurement Period Adjustment [Member]
ASSETS
Other current assets	524
Real estate held for development and sale	(2,000)
Property, plant and equipment	(5,132)
Timber and timberlands	913
Mineral rights	6,236
Trade name and customer relationships intangibles	500
Other long-term assets	1,546
Total assets acquired	2,587
LIABILITIES
Accounts payable and accrued liabilities	3,418
Deferred tax liabilities, net	(831)
Total liabilities assumed	$ 2,587