Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- References

No definition available.

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- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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Financial Instruments (Foreign Exchange Forward Contracts) (Details) - Foreign Exchange Forward [Member] CAD in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 CAD	Dec. 31, 2016 CAD	Dec. 31, 2015 CAD	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Foreign currency derivatives [Abstract]
Foreign exchange forward contracts notional amount \| $				$ 887	$ 1,035
Gain (Loss) on foreign exchange forward contracts	CAD (72)	CAD (1)	CAD 61
Other Current Assets [Member]
Foreign currency derivatives [Abstract]
Unrealized gain (loss) on foreign exchange forward contracts	0	19
Accounts Payable and Other [Member]
Foreign currency derivatives [Abstract]
Unrealized gain (loss) on foreign exchange forward contracts	CAD (19)	CAD (1)