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Employee Benefit Plans (Change in AOCI ) (Details) CAD in Millions	12 Months Ended
	Dec. 31, 2016 CAD
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	CAD 349
Balance, December 31	636
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	353
Amortized in current period, Net Actuarial Gain (Loss)	(42)
Current year addition to AOCI	19
Adjustments for MPS	0
Foreign currency translation adjustment	0
Balance, December 31	330
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	(4)
Amortized in current period, Net Prior Service Cost (Credit)	1
Current year addition to AOCI	0
Adjustments for MPS	0
Foreign currency translation adjustment	0
Balance, December 31	(3)
Pension Plan [Member] | Regulatory Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	0
Amortized in current period, Net Actuarial Gain (Loss)	(9)
Current year addition to AOCI	318
Adjustments for MPS	0
Foreign currency translation adjustment	0
Balance, December 31	309
Non-pension Benefit Plans [Member
Defined Benefit Plan Disclosure [Line Items]
Balance, January 1	(12)
Balance, December 31	44
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	15
Amortized in current period, Net Actuarial Gain (Loss)	(2)
Current year addition to AOCI	2
Adjustments for MPS	0
Foreign currency translation adjustment	0
Balance, December 31	15
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	(27)
Amortized in current period, Net Prior Service Cost (Credit)	8
Current year addition to AOCI	0
Adjustments for MPS	0
Foreign currency translation adjustment	0
Balance, December 31	(19)
Non-pension Benefit Plans [Member | Regulatory Assets [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	48
Adjustments for MPS	0
Foreign currency translation adjustment	0
Balance, December 31	CAD 48

X

- Definition

The pretax total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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Amount before tax, after reclassification adjustments, of actuarial gain (loss) that has not been recognized in the income statement.

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Amount before tax, after reclassification adjustments, of prior service cost (credit) that has not been recognized in the income statement.

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Amount before tax of gain (loss) adjustment to other comprehensive income (loss) resulting from settlement or curtailment of defined benefit pension and other postretirement defined benefit plans.

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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.

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