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Earnings Per Share Earnings Per Share (Tables) | 12 Months Ended
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Dec. 31, 2011
Earnings Per Share [Abstract] |
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] | Components of basic and diluted earnings per share are as follows:
| Years Ended December 31,
| 2011 |  | 2010 |  | 2009
Numerator (in millions): |  |  |  |  |
Net income attributable to Portland General Electric Company common shareholders | $ | 147 |  |  | $ | 125 |  |  | $ | 95 |
Denominator (in thousands): |  |  |  |  |
Weighted average common shares outstanding—basic | 75,333 |  |  | 75,275 |  |  | 72,790 |
Dilutive effect of unvested restricted stock units and employee stock purchase plan shares | 17 |  |  | 16 |  |  | 62 |
Weighted average common shares outstanding—diluted | 75,350 |  |  | 75,291 |  |  | 72,852 |
Earnings per share—basic and diluted | $ | 1.95 |  |  | $ | 1.66 |  |  | $ | 1.31 |
Basic and diluted earnings per share amounts are calculated based on actual amounts rather than the rounded amounts presented in the table above and on the consolidated statements of income. Accordingly, calculations using the rounded amounts presented for net income and weighted average shares outstanding may yield results that vary from the earnings per share amounts presented in the table above.

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- Definition Tabular disclosure of an entity's basic and diluted earnings per share calculations. + References No definition available. + Details
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