Condensed Consolidating Financial Information - Condensed Consolidating Statements of Income (Detail) - CAD CAD in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Freight									CAD 6,060	CAD 6,552	CAD 6,464
Non-freight									172	160	156
Total revenues	CAD 1,637	CAD 1,554	CAD 1,450	CAD 1,591	CAD 1,687	CAD 1,709	CAD 1,651	CAD 1,665	6,232	6,712	6,620
Operating expenses
Compensation and benefits									1,189	1,371	1,348
Fuel									567	708	1,048
Materials									180	184	193
Equipment rents									173	174	155
Depreciation and amortization									640	595	552
Purchased services and other									905	1,060	985
Gain on sale of Delaware & Hudson South									0	(68)	0
Total operating expenses									3,654	4,024	4,281
Operating income	717	657	551	653	677	753	646	612	2,578	2,688	2,339
Less:
Other income and charges									(45)	335	19
Net interest expense (income)									471	394	282
Income before income tax expense									2,152	1,959	2,038
Less: Income tax expense									553	607	562
Add: Equity in net earnings of subsidiaries									0	0	0
Net income	CAD 384	CAD 347	CAD 328	CAD 540	CAD 319	CAD 323	CAD 390	CAD 320	1,599	1,352	1,476
Consolidating Adjustments and Eliminations [Member]
Revenues
Freight									0	0	0
Non-freight									(348)	(331)	(331)
Total revenues									(348)	(331)	(331)
Operating expenses
Compensation and benefits									6	0	0
Fuel									0	0	0
Materials									18	0	0
Equipment rents									0	0	0
Depreciation and amortization									0	0	0
Purchased services and other									(372)	(331)	(331)
Gain on sale of Delaware & Hudson South										0
Total operating expenses									(348)	(331)	(331)
Operating income									0	0	0
Less:
Other income and charges									0	0	0
Net interest expense (income)									0	0	0
Income before income tax expense									0	0	0
Less: Income tax expense									0	0	0
Add: Equity in net earnings of subsidiaries									(2,098)	(2,175)	(2,037)
Net income									(2,098)	(2,175)	(2,037)
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member]
Revenues
Freight									0	0	0
Non-freight									0	0	0
Total revenues									0	0	0
Operating expenses
Compensation and benefits									0	0	0
Fuel									0	0	0
Materials									0	0	0
Equipment rents									0	0	0
Depreciation and amortization									0	0	0
Purchased services and other									0	0	0
Gain on sale of Delaware & Hudson South										0
Total operating expenses									0	0	0
Operating income									0	0	0
Less:
Other income and charges									(40)	84	3
Net interest expense (income)									1	(5)	0
Income before income tax expense									39	(79)	(3)
Less: Income tax expense									6	(21)	(1)
Add: Equity in net earnings of subsidiaries									1,566	1,410	1,478
Net income									1,599	1,352	1,476
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member]
Revenues
Freight									4,332	4,532	4,524
Non-freight									134	128	130
Total revenues									4,466	4,660	4,654
Operating expenses
Compensation and benefits									749	943	945
Fuel									458	549	779
Materials									130	148	156
Equipment rents									204	181	137
Depreciation and amortization									422	411	396
Purchased services and other									673	711	706
Gain on sale of Delaware & Hudson South										0
Total operating expenses									2,636	2,943	3,119
Operating income									1,830	1,717	1,535
Less:
Other income and charges									(34)	322	46
Net interest expense (income)									493	447	250
Income before income tax expense									1,371	948	1,239
Less: Income tax expense									337	303	320
Add: Equity in net earnings of subsidiaries									532	765	559
Net income									1,566	1,410	1,478
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenues
Freight									1,728	2,020	1,940
Non-freight									386	363	357
Total revenues									2,114	2,383	2,297
Operating expenses
Compensation and benefits									434	428	403
Fuel									109	159	269
Materials									32	36	37
Equipment rents									(31)	(7)	18
Depreciation and amortization									218	184	156
Purchased services and other									604	680	610
Gain on sale of Delaware & Hudson South										(68)
Total operating expenses									1,366	1,412	1,493
Operating income									748	971	804
Less:
Other income and charges									29	(71)	(30)
Net interest expense (income)									(23)	(48)	32
Income before income tax expense									742	1,090	802
Less: Income tax expense									210	325	243
Add: Equity in net earnings of subsidiaries									0	0	0
Net income									CAD 532	CAD 765	CAD 559