Condensed Consolidating Financial Information - Condensed Consolidating Statements of Cash Flows (Detail) - CAD CAD in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	CAD 2,459	CAD 2,123	CAD 1,950
Investing activities
Additions to properties	(1,522)	(1,449)	(1,236)
Proceeds from the sale of west end of Dakota, Minnesota and Eastern Railroad	0	236	0
Proceeds from the sale of Delaware & Hudson South	281	0	0
Proceeds from sale of properties and other assets	114	52	73
Advances to affiliates	0	0	0
Repayment of advances to affiliates	0	0	0
Capital contributions to affiliates	0	0	0
Change in restricted cash and cash equivalents used to collateralize letters of credit	0	411	(411)
Repurchase of share capital from affiliate	0
Other	4	0	(23)
Cash used in investing activities	(1,123)	(750)	(1,597)
Financing activities
Dividends paid	(226)	(244)	(244)
Issuance of share capital	0	0	0
Return of share capital to affiliates	0
Issuance of CP Common Shares	43	62	83
Purchase of CP common shares	(2,787)	(2,050)	0
Issuance of long-term debt, excluding commercial paper	3,411	0	0
Repayment of long-term debt, excluding commercial paper	(505)	(183)	(56)
Net issuance of commercial paper	(893)	771	0
Settlement of foreign exchange forward on long-term debt	0	17	0
Proceeds from Contributions from (Payments of Distributions to) Affiliates		0	0
Repayment of advances from affiliates	0	0	0
Other	0	(3)	(3)
Cash used in financing activities	(957)	(1,630)	(220)
Effect of foreign currency fluctuations on U.S. dollar-denominated cash and cash equivalents	45	7	10
Cash position
Increase (decrease) in cash and cash equivalents	424	(250)	143
Cash and cash equivalents at beginning of year	226	476	333
Cash and cash equivalents at end of year	650	226	476
Consolidating Adjustments and Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	(2,548)	(348)	(207)
Investing activities
Additions to properties	0	69	116
Proceeds from the sale of west end of Dakota, Minnesota and Eastern Railroad		0
Proceeds from the sale of Delaware & Hudson South	0
Proceeds from sale of properties and other assets	0	(69)	(116)
Advances to affiliates	3,264	3,247	137
Repayment of advances to affiliates	(1,804)	(3,759)	(84)
Capital contributions to affiliates	1,655	2,927	100
Change in restricted cash and cash equivalents used to collateralize letters of credit		0	0
Repurchase of share capital from affiliate	(1,210)
Other	0	0	0
Cash used in investing activities	1,905	2,415	153
Financing activities
Dividends paid	2,548	348	207
Issuance of share capital	(1,655)	(2,927)	(100)
Return of share capital to affiliates	1,210
Issuance of CP Common Shares	0	0	0
Purchase of CP common shares	0	0
Issuance of long-term debt, excluding commercial paper	0		0
Repayment of long-term debt, excluding commercial paper	0	0	0
Net issuance of commercial paper	0	0
Settlement of foreign exchange forward on long-term debt		0
Proceeds from Contributions from (Payments of Distributions to) Affiliates		(3,247)	(137)
Repayment of advances from affiliates	(3,264)	3,759	84
Other	1,804	0	0
Cash used in financing activities	643	(2,067)	54
Effect of foreign currency fluctuations on U.S. dollar-denominated cash and cash equivalents	0	0	0
Cash position
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of year	0	0	0
Cash and cash equivalents at end of year	0	0	0
CPRL (Parent Guarantor) [Member]
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	2,283	183	123
Investing activities
Additions to properties	0	0	0
Proceeds from the sale of west end of Dakota, Minnesota and Eastern Railroad		0
Proceeds from the sale of Delaware & Hudson South	0
Proceeds from sale of properties and other assets	0	0	0
Advances to affiliates	(1,133)	0	0
Repayment of advances to affiliates	0	0	0
Capital contributions to affiliates	0	0	0
Change in restricted cash and cash equivalents used to collateralize letters of credit		0	0
Repurchase of share capital from affiliate	0
Other	0	0	0
Cash used in investing activities	(1,133)	0	0
Financing activities
Dividends paid	(226)	(244)	(244)
Issuance of share capital	0	0	0
Return of share capital to affiliates	0
Issuance of CP Common Shares	43	62	83
Purchase of CP common shares	(2,787)	(2,050)
Issuance of long-term debt, excluding commercial paper	0		0
Repayment of long-term debt, excluding commercial paper	0	0	0
Net issuance of commercial paper	0	0
Settlement of foreign exchange forward on long-term debt		0
Proceeds from Contributions from (Payments of Distributions to) Affiliates		2,049	38
Repayment of advances from affiliates	1,820	0	0
Other	0	0	0
Cash used in financing activities	(1,150)	(183)	(123)
Effect of foreign currency fluctuations on U.S. dollar-denominated cash and cash equivalents	0	0	0
Cash position
Increase (decrease) in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of year	0	0	0
Cash and cash equivalents at end of year	0	0	0
CPRC (Subsidiary Issuer) [Member]
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	1,650	1,684	1,327
Investing activities
Additions to properties	(766)	(816)	(882)
Proceeds from the sale of west end of Dakota, Minnesota and Eastern Railroad		0
Proceeds from the sale of Delaware & Hudson South	0
Proceeds from sale of properties and other assets	103	116	65
Advances to affiliates	(311)	(611)	0
Repayment of advances to affiliates	804	2,167	0
Capital contributions to affiliates	(1,655)	(2,927)	(100)
Change in restricted cash and cash equivalents used to collateralize letters of credit		411	(411)
Repurchase of share capital from affiliate	1,210
Other	6	2	(21)
Cash used in investing activities	(609)	(1,658)	(1,349)
Financing activities
Dividends paid	(2,272)	(182)	(123)
Issuance of share capital	0	0	0
Return of share capital to affiliates	0
Issuance of CP Common Shares	0	0	0
Purchase of CP common shares	0	0
Issuance of long-term debt, excluding commercial paper	3,411		60
Repayment of long-term debt, excluding commercial paper	(461)	(174)	(48)
Net issuance of commercial paper	(893)	771
Settlement of foreign exchange forward on long-term debt		17
Proceeds from Contributions from (Payments of Distributions to) Affiliates		1,198	99
Repayment of advances from affiliates	500	(1,592)	(84)
Other	(1,000)	0	(3)
Cash used in financing activities	(715)	38	(99)
Effect of foreign currency fluctuations on U.S. dollar-denominated cash and cash equivalents	24	(3)	1
Cash position
Increase (decrease) in cash and cash equivalents	350	61	(120)
Cash and cash equivalents at beginning of year	152	91	211
Cash and cash equivalents at end of year	502	152	91
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash provided by operating activities	1,074	604	707
Investing activities
Additions to properties	(756)	(702)	(470)
Proceeds from the sale of west end of Dakota, Minnesota and Eastern Railroad		236
Proceeds from the sale of Delaware & Hudson South	281
Proceeds from sale of properties and other assets	11	5	124
Advances to affiliates	(1,820)	(2,636)	(137)
Repayment of advances to affiliates	1,000	1,592	84
Capital contributions to affiliates	0	0	0
Change in restricted cash and cash equivalents used to collateralize letters of credit		0	0
Repurchase of share capital from affiliate	0
Other	(2)	(2)	(2)
Cash used in investing activities	(1,286)	(1,507)	(401)
Financing activities
Dividends paid	(276)	(166)	(84)
Issuance of share capital	1,655	2,927	100
Return of share capital to affiliates	(1,210)
Issuance of CP Common Shares	0	0	0
Purchase of CP common shares	0	0
Issuance of long-term debt, excluding commercial paper	0		(60)
Repayment of long-term debt, excluding commercial paper	(44)	(9)	(8)
Net issuance of commercial paper	0	0
Settlement of foreign exchange forward on long-term debt		0
Proceeds from Contributions from (Payments of Distributions to) Affiliates		0	0
Repayment of advances from affiliates	944	(2,167)	0
Other	(804)	(3)	0
Cash used in financing activities	265	582	(52)
Effect of foreign currency fluctuations on U.S. dollar-denominated cash and cash equivalents	21	10	9
Cash position
Increase (decrease) in cash and cash equivalents	74	(311)	263
Cash and cash equivalents at beginning of year	74	385	122
Cash and cash equivalents at end of year	CAD 148	CAD 74	CAD 385