Environmental Matters - Environmental Sites $ in Thousands	1 Months Ended	6 Months Ended
	Jan. 31, 2017 USD ($)	Jun. 30, 2021 USD ($) party property	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)
Site Contingency [Line Items]
Current Liabilities		$ 22,514	$ 28,241	$ 34,066
Non-Current Liabilities		87,795	92,281	91,289
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities		6,658	7,596	10,431
Non-Current Liabilities		41,652	43,725	41,945
Site Contingency, Environmental Remediation Costs Recognized		48,300
Gasco/Siltronic Sediments | Minimum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost		48,300
Gasco/Siltronic Sediments | Maximum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost		350,000
Portland Harbor Other [Member]
Site Contingency [Line Items]
Current Liabilities		2,195	1,942	2,434
Non-Current Liabilities		$ 6,588	7,020	6,228
Gasco Uplands [Member]
Site Contingency [Line Items]
Site contingency: number of management pieces		2
Gasco/Siltronic Upland [Member]
Site Contingency [Line Items]
Current Liabilities		$ 12,442	14,887	10,979
Non-Current Liabilities		38,401	40,250	41,878
Front Street [Member]
Site Contingency [Line Items]
Current Liabilities		1,219	3,816	10,222
Non-Current Liabilities		975	1,107	1,059
Additional studies and design costs		2,200
Oregon Steel Mills [Member]
Site Contingency [Line Items]
Current Liabilities		0	0	0
Non-Current Liabilities		$ 179	$ 179	$ 179
Portland Harbor [Member]
Site Contingency [Line Items]
Number of potentially responsible parties (more than) | party		100
EPA final feasibility study and proposed remediation plan, clean-up costs, portland harbor	$ 1,050,000
Number of remediation projects | property		2
Portland Harbor [Member] | Minimum [Member]
Site Contingency [Line Items]
Percentage of clean-up costs	(30.00%)
Portland Harbor [Member] | Maximum [Member]
Site Contingency [Line Items]
Percentage of clean-up costs	50.00%
Yakama Nation [Member] | Portland Harbor Other [Member]
Site Contingency [Line Items]
Trustee Council Members - Number of Claimants		1
Site Contingency, Number of Other Third-Party Defendants		29
NRD liability claim yakama nation		$ 300
Number of Amended Complaints Filed		2