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Employee Benefit Plans (Change in AOCI ) (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 CAD ($)
Pension Plan [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Balance, January 1 | $ 636
Balance, December 31 | 563
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 | 330
Amortized in current period, Net Actuarial Gain (Loss) | (38)
Current year addition to AOCI | (8)
Balance, December 31 | 284
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 Prior Service Cost (Credit) | 0
Current year addition to AOCI | 0
Balance, December 31 | (3)
Pension Plan [Member] | Regulatory Assets [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Balance, January 1 | 309
Amortized in current period, Net Actuarial Gain (Loss) | (17)
Current year addition to AOCI | (10)
Balance, December 31 | 282
Non-pension Benefit Plans [Member |
Defined Benefit Plan Disclosure [Line Items] |
Balance, January 1 | 44
Balance, December 31 | 74
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)
Balance, December 31 | 11
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 | (19)
Amortized in current period, Net Prior Service Cost (Credit) | 8
Current year addition to AOCI | 0
Balance, December 31 | (11)
Non-pension Benefit Plans [Member | Regulatory Assets [Member] |
Defined Benefit Plan Disclosure [Line Items] |
Balance, January 1 | 48
Amortized in current period, Net Actuarial Gain (Loss) | 1
Current year addition to AOCI | 25
Balance, December 31 | $ 74

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- 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 + Details
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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 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=84228862&loc=SL7669646-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e637-108580 + Details
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