Earnings Per Common Share - Schedule of Earnings Per Share (EPS) (Details) - CAD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net Earnings to Common Shareholders
Basic EPS	$ 274	$ 720	$ 586	$ 1,031
Potential dilutive effect of stock options	0	0	0	0
Diluted EPS	$ 274	$ 720	$ 586	$ 1,031
Weighted Average Shares
Basic EPS (shares)	464.6	433.1	464.2	431.3
Potential dilutive effect of stock options (shares)	0.6	0.6	0.6	0.6
Diluted EPS (shares)	465.2	433.7	464.8	431.9
EPS
Basic (CAD per share)	$ 0.59	$ 1.66	$ 1.26	$ 2.39
Diluted (CAD per share)	$ 0.59	$ 1.66	$ 1.26	$ 2.39

Amount of increase (decrease) to net income used for calculating diluted earnings per share (EPS), resulting from the assumed exercise of stock options or restrictive stock units (RSUs).

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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