Cover Page Document - USD ($)
12 Months Ended
Dec. 31, 2019
Feb. 04, 2020
Jun. 30, 2019
Entity Incorporation, State or Country Code OR    
Document Transition Report false    
Document Annual Report true    
Entity Central Index Key 0000784977    
Document Type 10-K    
Document Period End Date Dec. 31, 2019    
Entity File Number 001-05532-99    
Entity Address, Address Line One 121 S.W. Salmon Street    
Entity Address, City or Town Portland    
Entity Address, State or Province OR    
Entity Address, Postal Zip Code 97204    
City Area Code 503    
Local Phone Number 464-8000    
Amendment Flag false    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Common Stock, Shares Outstanding   89,391,379  
Entity Public Float     $ 4,823,580,272
Entity Tax Identification Number 93-0256820    
Common Stock [Member]      
Title of 12(b) Security Common Stock, no par value    
Trading Symbol POR    
Security Exchange Name NYSE    
Medium-term Notes [Member]      
Title of 12(b) Security 9.31% Medium-Term Notes due 2021    
Trading Symbol POR 21    
Security Exchange Name NYSE