Nominal or face amount used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121590274&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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

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Financial Instruments (Foreign Exchange Forward Contracts) (Details) - Foreign Exchange Forward [Member] $ in Millions	12 Months Ended
	Dec. 31, 2020 CAD ($)	Dec. 31, 2019 CAD ($)	Dec. 31, 2018 CAD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Foreign Currency Derivatives [Abstract]
Notional amount				$ 397	$ 1,088
Gain (loss) on derivative instruments, net, pretax	$ (3,000,000)	$ (75,000,000)	$ 157,000,000
Other Current Assets [Member]
Foreign Currency Derivatives [Abstract]
Fair value of outstanding foreign exchange forward contracts	0	0
Accounts Payable and Other [Member]
Foreign Currency Derivatives [Abstract]
Fair value of outstanding foreign exchange forward contracts	$ 18,000,000	$ 24,000,000