Calculation of basic and diluted earnings per common share and the dividend declared by the company on its outstanding common shares (Detail) - CAD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income (loss) per common share - basic
Net income (loss)	$ 1,212	$ 196	$ 1,505	$ 712
Weighted average number of common shares outstanding (millions of shares)	767.4	816.1	772.5	822.6
Net income (loss) per common share (dollars)	$ 1.58	$ 0.24	$ 1.95	$ 0.86
Net income (loss) per common share - diluted
Net income (loss)	$ 1,212	$ 196	$ 1,505	$ 712
Weighted average number of common shares outstanding (millions of shares)	767.4	816.1	772.5	822.6
Effect of employee share-based awards (millions of shares)	2.5	2.7	2.4	2.6
Weighted average number of common shares outstanding, assuming dilution (millions of shares)	769.9	818.8	774.9	825.2
Net income (loss) per common share (dollars)	$ 1.57	$ 0.24	$ 1.94	$ 0.86
Dividends per common share - declared (dollars)	$ 0.22	$ 0.19	$ 0.41	$ 0.35