Condensed Consolidating Financial Information - Condensed Consolidating Statements of Income (Detail) - CAD CAD in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues
Freight										CAD 6,552	CAD 6,464	CAD 5,982
Non-freight										160	156	151
Total revenues	CAD 1,687	CAD 1,709	CAD 1,651	CAD 1,665	CAD 1,760	CAD 1,670	CAD 1,681	CAD 1,509		6,712	6,620	6,133
Operating expenses
Compensation and benefits										1,371	1,348	1,378
Fuel										708	1,048	1,004
Materials										184	193	160
Equipment rents										174	155	173
Depreciation and amortization										595	552	565
Purchased services and other										1,060	985	998
Gain on sale of Delaware & Hudson South										(68)	0	0
Asset impairment										0	0	435
Total operating expenses										4,024	4,281	4,713
Operating income	677	753	646	612	708	621	587	423		2,688	2,339	1,420
Less:
Other income and charges										335	19	17
Net interest (income) expense										394	282	278
Income before income tax expense										1,959	2,038	1,125
Less: Income tax (recovery) expense			23						CAD 7	607	562	250
Add: Equity in net earnings of subsidiaries										0	0	0
Net income	CAD 319	CAD 323	CAD 390	CAD 320	CAD 451	CAD 400	CAD 371	CAD 254		1,352	1,476	875
Consolidating Adjustments and Eliminations [Member]
Revenues
Freight										0	0	0
Non-freight										(331)	(331)	(341)
Total revenues										(331)	(331)	(341)
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										(331)	(331)	(341)
Gain on sale of Delaware & Hudson South										0
Asset impairment												0
Total operating expenses										(331)	(331)	(341)
Operating income										0	0	0
Less:
Other income and charges										0	0	0
Net interest (income) expense										0	0	0
Income before income tax expense										0	0	0
Less: Income tax (recovery) expense										0	0	0
Add: Equity in net earnings of subsidiaries										(2,175)	(2,037)	(1,056)
Net income										(2,175)	(2,037)	(1,056)
CPRL (Parent Guarantor) [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
Asset impairment												0
Total operating expenses										0	0	0
Operating income										0	0	0
Less:
Other income and charges										84	3	1
Net interest (income) expense										(5)	0	(1)
Income before income tax expense										(79)	(3)	0
Less: Income tax (recovery) expense										(21)	(1)	0
Add: Equity in net earnings of subsidiaries										1,410	1,478	875
Net income										1,352	1,476	875
CPRC (Subsidiary Issuer) [Member]
Revenues
Freight										4,532	4,524	4,201
Non-freight										128	130	128
Total revenues										4,660	4,654	4,329
Operating expenses
Compensation and benefits										943	945	1,021
Fuel										549	779	751
Materials										148	156	125
Equipment rents										181	137	150
Depreciation and amortization										411	396	416
Purchased services and other										711	706	690
Gain on sale of Delaware & Hudson South										0
Asset impairment												0
Total operating expenses										2,943	3,119	3,153
Operating income										1,717	1,535	1,176
Less:
Other income and charges										322	46	28
Net interest (income) expense										447	250	211
Income before income tax expense										948	1,239	937
Less: Income tax (recovery) expense										303	320	243
Add: Equity in net earnings of subsidiaries										765	559	181
Net income										1,410	1,478	875
Non-Guarantor Subsidiaries [Member]
Revenues
Freight										2,020	1,940	1,781
Non-freight										363	357	364
Total revenues										2,383	2,297	2,145
Operating expenses
Compensation and benefits										428	403	357
Fuel										159	269	253
Materials										36	37	35
Equipment rents										(7)	18	23
Depreciation and amortization										184	156	149
Purchased services and other										680	610	649
Gain on sale of Delaware & Hudson South										(68)
Asset impairment												435
Total operating expenses										1,412	1,493	1,901
Operating income										971	804	244
Less:
Other income and charges										(71)	(30)	(12)
Net interest (income) expense										(48)	32	68
Income before income tax expense										1,090	802	188
Less: Income tax (recovery) expense										325	243	7
Add: Equity in net earnings of subsidiaries										0	0	0
Net income										CAD 765	CAD 559	CAD 181