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Employee Benefit Plans (Change in AOCI ) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 CAD ($)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	$ 563
Balance, December 31	633
Pension Plan [Member] | Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	251
Amortized in current period, Net Actuarial Gain (Loss)	(37)
Current year addition to AOCI	32
Change in foreign exchange rate	0
Balance, December 31	246
Pension Plan [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	(3)
Amortized in current period, Net Actuarial Gain (Loss)	1
Current year addition to AOCI	0
Change in foreign exchange rate	0
Balance, December 31	(2)
Pension Plan [Member] | Regulatory Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	315
Amortized in current period, Net Actuarial Gain (Loss)	(26)
Current year addition to AOCI	73
Change in foreign exchange rate	27
Balance, December 31	389
Non-pension Benefit Plans [Member
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	74
Balance, December 31	58
Non-pension Benefit Plans [Member | Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	(4)
Amortized in current period, Net Actuarial Gain (Loss)	1
Current year addition to AOCI	(4)
Change in foreign exchange rate	0
Balance, December 31	(7)
Non-pension Benefit Plans [Member | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	0
Amortized in current period, Net Actuarial Gain (Loss)	0
Current year addition to AOCI	0
Change in foreign exchange rate	0
Balance, December 31	0
Non-pension Benefit Plans [Member | Regulatory Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	78
Amortized in current period, Net Actuarial Gain (Loss)	2
Current year addition to AOCI	(17)
Change in foreign exchange rate	2
Balance, December 31	$ 65

X

- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14A
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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- Definition

Amount, before tax, after reclassification adjustment, of increase (decrease) in accumulated other comprehensive income from gain (loss) of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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-Paragraph 10A
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-URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580

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-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580

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Amount before tax, after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 35
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=82918529&loc=d3e30304-110892

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