Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The amount that best represents the maximum exposure to credit risk without taking into account any collateral held or other credit enhancements (for example, netting agreements that do not qualify for offset in accordance with IAS 32). [Refer: Credit risk [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2018-01-01
-Paragraph 35K
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_35K_a&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2021-01-01
-Name IFRS
-Number 7
-IssueDate 2018-01-01
-Paragraph 36
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_36_a&doctype=Standard&book=b
-URIDate 2018-03-16

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of current trade receivables and current other receivables. [Refer: Current trade receivables; Other current receivables]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 54
-Subparagraph h
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_54_h&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
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-IssueDate 2018-01-01
-Paragraph 78
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_78_b&doctype=Standard
-URIDate 2018-03-16

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Credit Risk, Allocation Percentage

+ References

No definition available.

+ Details

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Namespace Prefix:	tac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=tac_LongtermPortionOfFinanceLeaseReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=ifrs-full_LoansAndReceivablesCategoryMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	ifrs-full_ExternalCreditGradesAxis=tac_InvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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- Details

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Risk Management Activities - Credit Risk (Details) - CAD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	$ 5	$ 13
Trade and other receivables	462	$ 756
Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	$ 1,491
Credit risk \| Trade and other receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Credit risk \| Long-term portion of finance lease receivable
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Maximum exposure to credit risk	$ 176
Credit risk \| Risk management assets
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Maximum exposure to credit risk	$ 806
Credit risk \| Amortized cost
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Maximum exposure to credit risk	$ 47
Credit risk \| Investment Grade [Member] \| Trade and other receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	85.00%
Credit risk \| Investment Grade [Member] \| Long-term portion of finance lease receivable
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Credit risk \| Investment Grade [Member] \| Risk management assets
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	99.00%
Credit risk \| Investment Grade [Member] \| Amortized cost
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	0.00%
Credit risk \| Non-Investment Grade [Member] \| Trade and other receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	15.00%
Credit risk \| Non-Investment Grade [Member] \| Long-term portion of finance lease receivable
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	0.00%
Credit risk \| Non-Investment Grade [Member] \| Risk management assets
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	1.00%
Credit risk \| Non-Investment Grade [Member] \| Amortized cost
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Trade and other receivables \| Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	$ 462