Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Components of Earnings per Share [Abstract]
stock offering	11,100,000
Unvested performance based restricted stock	435,224	466,624	435,224	466,624
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	228,000
Numerator (in millions)
Net income sttributable to Portland General Electric Company common shareholders	$ (22)	$ 26		$ 75
Denominator
Weighted Average Common Shares Outstanding-Basic	75,935,000	75,507,000	75,772,000	75,465,000
Dilutive effect of unvested restricted stock units and employee stock purchase plan shares	0	10,000	121,000	14,000
Weighted Average Common Shares Outstanding-Diluted	75,935,000	75,517,000	75,893,000	75,479,000
Earnings (loss) per share:
Earnings Per Share, Basic and Diluted	$ (0.29)	$ 0.34	$ 0.36	$ 0.99

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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