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Common Shares (Tables) | 12 Months Ended
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Dec. 31, 2019
Share Capital, Reserves And Other Equity Interest [Abstract] |
Issued and outstanding | TransAlta is authorized to issue an unlimited number of voting common shares without nominal or par value.
As at Dec. 31 | 2019 |  | 2018 |
| Common shares (millions) | Amount | Common shares (millions) | Amount
Issued and outstanding, beginning of year | 284.6 |  | 3,059 |  | 287.9 |  | 3,094 |
Purchased and cancelled under the NCIB | (7.7) |  | (83) |  | (3.3) |  | (35) |
Stock options exercised | 0.1 |  | 2 |  | — |  | — |
Issued and outstanding, end of year | 277.0 |  | 2,978 |  | 284.6 |  | 3,059 |
The following are the effects of the Corporation's purchase and cancellation of the common shares during the year:
For the year ended Dec. 31 | 2019 | 2018
Total shares purchased(1) | 7,716,300 |  | 3,264,500 |
Average purchase price per share | $ | 8.80 |  | $ | 7.02 |
Total cost | 68 |  | 23 |
Weighted average book value of shares cancelled | 83 |  | 35 |
Amount recorded in deficit | 15 |  | 12 |
All preferred shares issued and outstanding are non-voting cumulative redeemable fixed rate first preferred shares.
As at Dec. 31 | 2019 |  | 2018 |
Series | Number of shares (millions) | Amount | Number of shares (millions) | Amount
Series A | 10.2 |  | 248 |  | 10.2 |  | 248 |
Series B | 1.8 |  | 45 |  | 1.8 |  | 45 |
Series C | 11.0 |  | 269 |  | 11.0 |  | 269 |
Series E | 9.0 |  | 219 |  | 9.0 |  | 219 |
Series G | 6.6 |  | 161 |  | 6.6 |  | 161 |
Issued and outstanding, end of year | 38.6 |  | 942 |  | 38.6 |  | 942 |
Earnings per share |
Year ended Dec. 31 | 2019 | 2018 | 2017
Net earnings (loss) attributable to common shareholders | 52 |  | (248) |  | (190) |
Basic and diluted weighted average number of common shares outstanding (millions) | 283 |  | 287 |  | 288 |
Net earnings (loss) per share attributable to common shareholders, basic and diluted | 0.18 |  | (0.86) |  | (0.66) |

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