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Stock-based Compensatin (Stock Options) (Details) - CAD ($)
$ / shares in Units, $ in Millions

12 Months Ended

Dec. 31, 2018

Dec. 31, 2017

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]

Exercised

(20,000)

(100,000)

Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period

20,000

100,000

Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 1.7

$ 2.37

Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options

$ 5

$ 3

Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition

2 years 2 months 13 days

2 years 6 months

Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term

5 years 1 month 6 days

5 years 4 months 25 days

Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value

$ 18

$ 22

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value

$ 2

$ 2

Employee Stock Option [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]

Beginning Balance

3,643,575

Granted

627,600

Exercised

(23,800)

Forfeited

(11,700)

Expired

(10,100)

Ending Balance

4,225,575

3,643,575

Options exercisable

^[1],[2]

2,546,250

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]

Beginning Balance

$ 39.42

Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price

39.93

Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price

24.98

ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice

45.1

ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice

39.93

Ending Balance

39.56

$ 39.42

Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price

$ 37.15

Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross

627,600

Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period

23,800

Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]

Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price

$ 24.98

Employee Non-vested Stock Option [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]

Granted

627,600

Vested

(666,125)

Forfeited

(11,700)

Expired

(10,100)

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]

Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price

$ 1.7

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value

2.51

ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice

2.54

ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice

$ 1.7

Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]

Beginning Balance

^[3]

1,739,650

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross

627,600

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares

666,125

Ending Balance

1,679,325

1,739,650

^[3]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]

Beginning Balance

$ 2.52

Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Options Forfeited Weighted Average Grant Date Fair Value

2.54

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Grant Date Fair Value

2.51

Ending Balance

$ 2.22

$ 2.52

[1]	As at December 31, 2018, the fair value of options that vested in the year was $2 million (2017 - $2 million).
[2]	As at December 31, 2018, the weighted average remaining term of vested options was 5.1 years with an aggregate intrinsic value of $18 million (2017 - 5.4 years, $22 million).
[3]	As at December 31, 2018, there was $5 million of unrecognized compensation related to stock options not yet vested which is expected to be recognized over a weighted average period of approximately 2.2 years (2017 - $3 million, 2.5 years).

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+ References

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