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Non-Controlling Interests - Financial Position of Non-Controlling Interests (Details) - CAD | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of subsidiaries [line items] |  |  |
Current assets | CAD 1,709,000,000 | CAD 1,554,000,000 |
Current liabilities | 1,608,000,000 | 1,217,000,000 |
Total equity | 4,385,000,000 | 4,663,000,000 | CAD 4,390,000,000
Non-controlling interests (Note 11) | 1,059,000,000 | 1,152,000,000 |
TransAlta Renewables |  |  |
Disclosure of subsidiaries [line items] |  |  |
Current assets | 145,000,000 | 109,000,000 |
Long-term assets | 3,483,000,000 | 3,732,000,000 |
Current liabilities | (356) | (537,000,000) |
Long-term liabilities | (1,075,000,000) | (1,237,000,000) |
Total equity | (2,197,000,000) | (2,067,000,000) |
Non-controlling interests (Note 11) | CAD (812,000,000) | CAD (851,000,000) |
Ownership and voting rights percentage | 36.00% | 40.20% |
TransAlta Cogeneration L.P. |  |  |
Disclosure of subsidiaries [line items] |  |  |
Current assets | CAD 193,000,000 | CAD 171,000,000 |
Long-term assets | 404,000,000 | 538,000,000 |
Current liabilities | (73) | (65,000,000) |
Long-term liabilities | (26) | (35,000,000) |
Total equity | (498) | (609,000,000) |
Non-controlling interests (Note 11) | CAD (247,000,000) | CAD (301,000,000) |
Ownership and voting rights percentage | 49.99% | 49.99% |
TransAlta Cogeneration L.P. | Coal facility |  |  |
Disclosure of subsidiaries [line items] |  |  |
Ownership and voting rights percentage | 5000.00% |  |

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