Document and Entity Information Document - shares	9 Months Ended
	Sep. 30, 2021	Oct. 19, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2021
Document Period End Date	Sep. 30, 2021
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-01342
Entity Registrant Name	CANADIAN PACIFIC RAILWAY LTD/CN
Entity Central Index Key	0000016875
Entity Incorporation, State or Country Code	Z4
Entity Tax Identification Number	98-0355078
Entity Address, Address Line One	7550 Ogden Dale Road S.E.
Entity Address, City or Town	Calgary
Entity Address, State or Province	AB
Entity Address, Postal Zip Code	T2C 4X9
City Area Code	(403)
Local Phone Number	319-7000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		666,964,525
Common Shares, without par value, of Canadian Pacific Railway Limited
Entity Information [Line Items]
Title of 12(b) Security	Common Shares, without par value, of Canadian Pacific Railway Limited
Trading Symbol	CP
Security Exchange Name	NYSE
Perpetual 4% Consolidated Debenture Stock of Canadian Pacific Railway Company
Entity Information [Line Items]
Title of 12(b) Security	Perpetual 4% Consolidated Debenture Stock of Canadian Pacific Railway Company
Trading Symbol	CP/40
Security Exchange Name	NYSE