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	710				710
Other comprehensive (loss) income	86			86
Dividends declared	(115)				(115)
Effect of stock-based compensation expense	10		10
CP Common Shares repurchased (shares)		(5.2)
CP Common Shares repurchased	(1,080)	CAD (70)			(1,010)
Shares issued under stock option plan (shares)		0.4
Shares issued under stock option plan	CAD 30	CAD 36	(6)
Ending balance (shares) at Jun. 30, 2015	161.3	161.3
Ending balance at Jun. 30, 2015	CAD 5,251	CAD 2,151	40	(2,133)	5,193
Beginning balance at Mar. 31, 2015				(2,207)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	390
Other comprehensive (loss) income	CAD 74
Ending balance (shares) at Jun. 30, 2015	161.3	161.3
Ending balance at Jun. 30, 2015	CAD 5,251	CAD 2,151	40	(2,133)	5,193
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	868				868
Other comprehensive (loss) income	6			6
Dividends declared	(130)				(130)
Effect of stock-based compensation expense	8		8
CP Common Shares repurchased (shares)		(4.7)
CP Common Shares repurchased	(867)	CAD (70)			(797)
Shares issued under stock option plan (shares)		0.1
Shares issued under stock option plan	CAD 10	CAD 12	(2)
Ending balance (shares) at Jun. 30, 2016	148.4	148.4
Ending balance at Jun. 30, 2016	CAD 4,691	CAD 2,000	49	(1,471)	4,113
Beginning balance at Mar. 31, 2016				(1,481)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	328
Other comprehensive (loss) income	CAD 10
Ending balance (shares) at Jun. 30, 2016	148.4	148.4
Ending balance at Jun. 30, 2016	CAD 4,691	CAD 2,000	CAD 49	CAD (1,471)	CAD 4,113