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Employee Benefit Plans (Assumptions Used in Accounting for Defined Benefit Pension and Other Post-retirement Benefit Plans) (Details) - CAD CAD in Millions | 12 Months Ended
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Dec. 31, 2016 | Dec. 31, 2015
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract] |  |
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components | CAD 1 |
Defined Benefit Plan, Effect of One Percentage Point Decrease on Service and Interest Cost Components | 1 |
Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation | 20 |
Defined Benefit Plan, Effect of One Percentage Point Decrease on Accumulated Postretirement Benefit Obligation | 17 |
Defined Benefit Plan, Assumptions Used in Calculations [Abstract] |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Increase | (7) |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Decrease | 7 |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Asset Rate Increase | (4) |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Asset Rate Decrease | CAD 4 |
Pension Plan [Member] |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate | 3.96% | 4.02%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase | 2.82% | 3.07%
Defined Benefit Plan, Benefit Obligation, Health Care Cost Trend Rate Assumed for Next Fiscal Year | 0.00% | 0.00%
Defined Benefit Plan, Benefit Obligation, Ultimate Health Care Cost Trend Rate | 0.00% | 0.00%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate | 3.79% | 3.99%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets | 6.33% | 5.91%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase | 2.88% | 3.07%
Defined Benefit Plan, Net Periodic Benefit Cost, Health Care Cost Trend Rate Assumed for Next Fiscal Year | 0.00% | 0.00%
Defined Benefit Plan, Net Periodic Benefit Cost, Ultimate Health Care Cost Trend Rate | 0.00% | 0.00%
Non-pension Benefit Plans [Member |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate | 4.18% | 4.04%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase | 2.54% | 3.50%
Defined Benefit Plan, Benefit Obligation, Health Care Cost Trend Rate Assumed for Next Fiscal Year | 6.78% | 5.50%
Defined Benefit Plan, Benefit Obligation, Ultimate Health Care Cost Trend Rate | 4.45% | 4.20%
Defined Benefit Plan, Benefit Obligation, Year that Rate Reaches Ultimate Trend Rate | 2020 | 2020
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate | 3.88% | 3.98%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets | 4.43% | 0.00%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase | 2.56% | 3.50%
Defined Benefit Plan, Net Periodic Benefit Cost, Health Care Cost Trend Rate Assumed for Next Fiscal Year | 6.76% | 5.90%
Defined Benefit Plan, Net Periodic Benefit Cost, Ultimate Health Care Cost Trend Rate | 4.45% | 4.30%
Defined Benefit Plan, Net Periodic Benefit Cost, Year that Rate Reaches Ultimate Trend Rate | 2020 | 2020

X
- Definition The decrease in plan assets based on a 25 basis points (0.25 percent) change. + References No definition available. + Details
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- Definition The increase in plan assets based on a 25 basis points (0.25 percent) change. + References No definition available. + Details
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- Definition The decrease from a 25 basis points (0.25 percent) change on the discount rate. + References No definition available. + Details
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- Definition The increase from a 25 basis points (0.25 percent) change on the discount rate. + References No definition available. + Details
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- Definition The assumed health care related to benefit obligation trend rate for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. + References No definition available. + Details
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- Definition The ultimate trend rate for health care costs related to benefit obligation. + References No definition available. + Details
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- Definition Year the ultimate health care cost trend rate related to benefit obligation is expected to be reached, in CCYY format. + References No definition available. + Details
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- Definition The assumed health care cost trend rate related to net periodic benefits costs for the next year used to measure the expected cost of benefits covered by the plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. + References No definition available. + Details
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- Definition The ultimate trend rate for health care costs related to net periodic benefits costs. + References No definition available. + Details
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- Definition Year the ultimate health care cost trend rate related to net periodic benefits costs is expected to be reached, in CCYY format. + References No definition available. + Details
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- Definition The interest rate used to adjust for the time value of money for the 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Expected rate of compensation increases (for pay-related plans). + 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 (k)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The interest rate used to adjust for the time value of money. + 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Expected Long-Term Rate of Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512046 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Expected rate of compensation increases (for pay-related plans). + 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 (k)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- References No definition available. + Details
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- Definition Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits. + 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 (m) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs. + 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 (m) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits. + 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 (m) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs. + 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 (m) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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