Environmental Matters - Environmental Sites $ in Thousands	1 Months Ended	9 Months Ended
	Jan. 31, 2017 USD ($)	Sep. 30, 2020 USD ($) party property	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)
Site Contingency [Line Items]
Current Liabilities		$ 30,483	$ 39,225	$ 22,403
Non-Current Liabilities		92,129	96,797	96,662
Gasco/Siltronic Sediments
Site Contingency [Line Items]
Current Liabilities		8,338	11,632	5,976
Non-Current Liabilities		43,509	46,082	43,861
Site Contingency, Environmental Remediation Costs Recognized		51,800
Gasco/Siltronic Sediments | Minimum [Member]
Site Contingency [Line Items]
Environmental Exit Costs, Anticipated Cost		51,800
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		2,760	2,543	2,211
Non-Current Liabilities		$ 5,882	6,920	5,331
Gasco Uplands [Member]
Site Contingency [Line Items]
Site contingency: number of management pieces		2
Gasco/Siltronic Upland [Member]
Site Contingency [Line Items]
Current Liabilities		$ 8,775	14,203	8,202
Non-Current Liabilities		41,515	43,616	42,267
Central Service Center [Member]
Site Contingency [Line Items]
Current Liabilities		0	0	5
Non-Current Liabilities		$ 0	0	0
Environmental monitoring activities, duration		5 years
Front Street [Member]
Site Contingency [Line Items]
Current Liabilities		$ 10,610	10,847	6,009
Non-Current Liabilities		1,044	0	5,024
Undiscounted environmental remediation expense		7,100
Additional studies and design costs		4,600
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