Non-Controlling Interests - Share of Ownership and Equity Participation in TransAlta Renewables (Details) - TransAlta Renewables	1 Months Ended	5 Months Ended	7 Months Ended	12 Months Ended	19 Months Ended
Jan. 05, 2016	Dec. 31, 2017	Nov. 25, 2015	May 06, 2015	Jul. 31, 2017
Disclosure of subsidiaries [line items]
Equity participation percentage	66.60%	64.00%	76.10%	70.30%	64.00%
Proportion of equity participation in subsidiary	62.00%	64.00%	72.80%	70.30%	59.80%

The proportion of ownership interest in a subsidiary attributable to the entity. [Refer: Subsidiaries [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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