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

Name:	ifrs-full_DisclosureOfCreditRiskExposureLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
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
-Note Effective 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 35K
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-01&anchor=para_35K_a&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-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 2017-03-09

+ Details

Name:	ifrs-full_MaximumExposureToCreditRisk
Namespace Prefix:	ifrs-full_
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 2017-01-01
-Paragraph 54
-Subparagraph h
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_h&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 78
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_78_b&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_TradeAndOtherCurrentReceivables
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Credit Risk, Allocation Percentage

+ References

No definition available.

+ Details

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

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CreditRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=tac_TradeAndOtherReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=tac_RiskManagementAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	ifrs-full_ExternalCreditGradesAxis=tac_NonInvestmentGradeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfFinancialAssetsAxis=tac_TradeAndOtherReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Risk Management Activities - Credit Risk (Details) - CAD number in Thousands, CAD in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	CAD 40	CAD 14
Trade and other receivables	933	CAD 703
Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	2,084
Trade and other receivables	CAD 5
Credit risk \| Trade and other receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	10000.00%
Credit risk \| Long-term portion of finance lease receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	10000.00%
Maximum exposure to credit risk	CAD 215
Credit risk \| Risk management assets
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	10000.00%
Maximum exposure to credit risk	CAD 903
Credit risk \| Loans and receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	10000.00%
Maximum exposure to credit risk	CAD 33
Credit risk \| Investment Grade [Member] \| Trade and other receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	8700.00%
Credit risk \| Investment Grade [Member] \| Long-term portion of finance lease receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	9600.00%
Credit risk \| Investment Grade [Member] \| Risk management assets
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	9900.00%
Credit risk \| Investment Grade [Member] \| Loans and receivables
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	1300.00%
Credit risk \| Non-Investment Grade [Member] \| Long-term portion of finance lease receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	400.00%
Credit risk \| Non-Investment Grade [Member] \| Risk management assets
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	100.00%
Credit risk \| Non-Investment Grade [Member] \| Loans and receivables
Disclosure of credit risk exposure [line items]
Credit risk, allocation percentage	10000.00%
Trade and other receivables \| Credit risk
Disclosure of credit risk exposure [line items]
Maximum exposure to credit risk	CAD 933