CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - CAD ($) $ in Millions	Total	Share capital [Member]	Additional paid-in capital [Member]	Accumulated other comprehensive loss [Member]	Retained earnings [Member]
Beginning Balance at Dec. 31, 2015	$ 4,796	$ 2,058	$ 43	$ (1,477)	$ 4,172
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,599	0	0	0	1,599
Other comprehensive income (loss)	(322)	0	0	(322)	0
Dividends declared	(274)	0	0	0	(274)
Effect of stock-based compensation expense	14	0	14	0	0
CP Common Shares repurchased	(1,210)	(84)	0	0	(1,126)
Stock issued under stock option plan	23	28	(5)	0	0
Ending Balance at Dec. 31, 2016	4,626	2,002	52	(1,799)	4,371
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,405	0	0	0	2,405
Other comprehensive income (loss)	58	0	0	58	0
Dividends declared	(319)	0	0	0	(319)
Effect of stock-based compensation expense	3	0	3	0	0
CP Common Shares repurchased	(381)	(27)	0	0	(354)
Stock issued under stock option plan	45	57	(12)	0	0
Ending Balance at Dec. 31, 2017	6,437	2,032	43	(1,741)	6,103
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,951	0	0	0	1,951
Other comprehensive income (loss)	(302)	0	0	(302)	0
Dividends declared	(358)	0	0	0	(358)
Effect of stock-based compensation expense	11	0	11	0	0
CP Common Shares repurchased	(1,127)	(66)	0	0	(1,061)
Stock issued under stock option plan	24	36	(12)	0	0
Ending Balance at Dec. 31, 2018	$ 6,636	$ 2,002	$ 42	$ (2,043)	$ 6,635