Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 17, 2021	Jun. 30, 2020
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Document Period End Date	Dec. 31, 2020
Entity Registrant Name	CANADIAN PACIFIC RAILWAY LTD/CN
Entity Central Index Key	0000016875
Entity File Number	001-01342
Entity Tax Identification Number	98-0355078
Entity Incorporation, State or Country Code	Z4
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 Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Entity Public Float			$ 34,600,245,541
Entity Common Stock, Shares Outstanding		133,297,236
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