INTERIM CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (unaudited) - CAD shares in Millions, CAD in Millions	Total	Common shares/Share capital [Member]	Additional paid-in capital [Member]	Accumulated other comprehensive loss [Member]	Retained earnings [Member]
Beginning balance (shares) at Dec. 31, 2014		166.1
Beginning balance at Dec. 31, 2014	CAD 5,610	CAD 2,185	CAD 36	CAD (2,219)	CAD 5,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,033				1,033
Other comprehensive (loss) income	106			106
Dividends declared	(170)				(170)
Effect of stock-based compensation expense	14		14
CP Common Shares repurchased (shares)		(12.7)
CP Common Shares repurchased	(2,635)	CAD (173)			(2,462)
Shares issued under stock option plan (shares)		0.4
Shares issued under stock option plan	CAD 34	CAD 42	(8)
Ending balance (shares) at Sep. 30, 2015	153.8	153.8
Ending balance at Sep. 30, 2015	CAD 3,992	CAD 2,054	42	(2,113)	4,009
Beginning balance at Jun. 30, 2015				(2,133)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	323
Other comprehensive (loss) income	CAD 20
Ending balance (shares) at Sep. 30, 2015	153.8	153.8
Ending balance at Sep. 30, 2015	CAD 3,992	CAD 2,054	42	(2,113)	4,009
Beginning balance (shares) at Dec. 31, 2015		153.0
Beginning balance at Dec. 31, 2015	4,796	CAD 2,058	43	(1,477)	4,172
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,215				1,215
Other comprehensive (loss) income	44			44
Dividends declared	(202)				(202)
Effect of stock-based compensation expense	11		11
CP Common Shares repurchased (shares)		(6.9)
CP Common Shares repurchased	(1,210)	CAD (84)			(1,126)
Shares issued under stock option plan (shares)		0.2
Shares issued under stock option plan	CAD 15	CAD 26	(11)
Ending balance (shares) at Sep. 30, 2016	146.3	146.3
Ending balance at Sep. 30, 2016	CAD 4,669	CAD 2,000	43	(1,433)	4,059
Beginning balance at Jun. 30, 2016				(1,471)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	347
Other comprehensive (loss) income	CAD 38
Ending balance (shares) at Sep. 30, 2016	146.3	146.3
Ending balance at Sep. 30, 2016	CAD 4,669	CAD 2,000	CAD 43	CAD (1,433)	CAD 4,059