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	1,848	0	0	0	1,848
Other comprehensive income	23	0	0	23	0
Dividends declared	(253)	0	0	0	(253)
Effect of stock-based compensation expense	$ 12	0	12	0	0
Shares issued under stock option plan (shares)	0.5
Shares issued under stock option plan	$ 16	20	(4)	0	0
Ending balance (shares) at Jun. 30, 2021	666.8
Ending balance at Jun. 30, 2021	$ 8,965	2,003	63	(2,791)	9,690
Beginning balance (shares) at Mar. 31, 2021	666.6
Beginning balance at Mar. 31, 2021	$ 7,866	1,993	58	(2,756)	8,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,246	0	0	0	1,246
Other comprehensive income	(35)	0	0	(35)	0
Dividends declared	(127)	0	0	0	(127)
Effect of stock-based compensation expense	$ 7	0	7	0	0
Shares issued under stock option plan (shares)	0.2
Shares issued under stock option plan	$ 8	10	(2)	0	0
Ending balance (shares) at Jun. 30, 2021	666.8
Ending balance at Jun. 30, 2021	$ 8,965	2,003	63	(2,791)	9,690
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	1,355	0	0	0	1,355
Other comprehensive income	564	0	0	564	0
Dividends declared	(354)	0	0	0	(354)
Effect of stock-based compensation expense	12	0	12	0	0
Shares issued for Kansas City Southern acquisition	$ (2)	0	(2)	0	0
Shares issued under stock option plan (shares)	0.3
Shares issued under stock option plan	$ 10	13	(3)	0	0
Ending balance (shares) at Jun. 30, 2022	930.0
Ending balance at Jun. 30, 2022	$ 35,414	25,488	73	(1,539)	11,392
Beginning balance (shares) at Mar. 31, 2022	929.9
Beginning balance at Mar. 31, 2022	$ 33,985	25,486	68	(2,373)	10,804
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	765	0	0	0	765
Other comprehensive income	834	0	0	834	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	$ 2	2	0	0	0
Ending balance (shares) at Jun. 30, 2022	930.0
Ending balance at Jun. 30, 2022	$ 35,414	$ 25,488	$ 73	$ (1,539)	$ 11,392