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Short Term Debt (Short-term debt and the related weighted-average interest rates) (Details) - CAD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Short-term Debt	$ 1,241	$ 961
Short-term Debt, Weighted Average Interest Rate	2.42%	1.73%
TECO Energy Inc. and TECO Finance Inc. [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 820	$ 685
Short-term Debt, Weighted Average Interest Rate	2.58%	1.74%
Tampa Electric Division [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 382	$ 228
Short-term Debt, Weighted Average Interest Rate	2.07%	1.49%
New Mexico Gas Company [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 38	$ 35
Short-term Debt, Weighted Average Interest Rate	2.47%	1.71%
Nova Scotia Power Inc. [Member] | Notes Payable to Banks [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 1	$ 1
Short-term Debt, Weighted Average Interest Rate	0.00%	0.00%
Grand Bahama Power Company Limited [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Short-term Debt	$ 0	$ 12
Short-term Debt, Weighted Average Interest Rate	0.00%	5.75%

X

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

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+ References

No definition available.

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- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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