INTERIM CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (unaudited) - CAD ($) shares in Millions, $ in Millions	Total	Share capital	Additional paid-in capital	Accumulated other comprehensive loss	Retained earnings
Beginning balance (shares) at Dec. 31, 2020	666.3
Beginning balance at Dec. 31, 2020	$ 7,319	$ 1,983	$ 55	$ (2,814)	$ 8,095
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,320	0	0	0	2,320
Other comprehensive income	171	0	0	171	0
Dividends declared	(380)	0	0	0	(380)
Effect of stock-based compensation expense	$ 18	0	18	0	0
Shares issued under stock option plan (shares)	0.6
Shares issued under stock option plan	$ 20	25	(5)	0	0
Ending balance (shares) at Sep. 30, 2021	666.9
Ending balance at Sep. 30, 2021	$ 9,468	2,008	68	(2,643)	10,035
Beginning balance (shares) at Jun. 30, 2021	666.8
Beginning balance at Jun. 30, 2021	$ 8,965	2,003	63	(2,791)	9,690
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	472	0	0	0	472
Other comprehensive income	148	0	0	148	0
Dividends declared	(127)	0	0	0	(127)
Effect of stock-based compensation expense	$ 6	0	6	0	0
Shares issued under stock option plan (shares)	0.1
Shares issued under stock option plan	$ 4	5	(1)	0	0
Ending balance (shares) at Sep. 30, 2021	666.9
Ending balance at Sep. 30, 2021	$ 9,468	2,008	68	(2,643)	10,035
Beginning balance (shares) at Dec. 31, 2021	929.7
Beginning balance at Dec. 31, 2021	$ 33,829	25,475	66	(2,103)	10,391
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,246	0	0	0	2,246
Other comprehensive income	2,236	0	0	2,236	0
Dividends declared	(531)	0	0	0	(531)
Effect of stock-based compensation expense	17	0	17	0	0
Shares issued for Kansas City Southern acquisition	$ (2)	0	(2)	0	0
Shares issued under stock option plan (shares)	0.4
Shares issued under stock option plan	$ 19	23	(4)	0	0
Ending balance (shares) at Sep. 30, 2022	930.1
Ending balance at Sep. 30, 2022	$ 37,814	25,498	77	133	12,106
Beginning balance (shares) at Jun. 30, 2022	930.0
Beginning balance at Jun. 30, 2022	$ 35,414	25,488	73	(1,539)	11,392
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	891	0	0	0	891
Other comprehensive income	1,672	0	0	1,672	0
Dividends declared	(177)	0	0	0	(177)
Effect of stock-based compensation expense	$ 5	0	5	0	0
Shares issued under stock option plan (shares)	0.1
Shares issued under stock option plan	$ 9	10	(1)	0	0
Ending balance (shares) at Sep. 30, 2022	930.1
Ending balance at Sep. 30, 2022	$ 37,814	$ 25,498	$ 77	$ 133	$ 12,106