Condensed Consolidating Financial Information - Interim Condensed Consolidating Statements of Income (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues
Total revenues	$ 2,043	$ 1,767
Operating expenses
Compensation and benefits	398	406
Fuel	212	209
Materials	59	57
Equipment rents	36	35
Depreciation and amortization	192	160
Purchased services and other	312	357
Total operating expenses	1,209	1,224
Operating income	834	543
Less:
Other expense (income)	211	(47)
Other components of net periodic benefit recovery cost	(85)	(97)
Net interest (income) expense	114	114
(Loss) income before income tax expense and equity in net earnings of subsidiaries	594	573
Income tax expense (recovery)	185	139
Add: Equity in net earnings of subsidiaries	0	0
Net income	409	434
Freight
Revenues
Total revenues	2,000	1,726
Non-freight
Revenues
Total revenues	43	41
Consolidating Adjustments and Eliminations [Member]
Revenues
Total revenues	(83)	(102)
Operating expenses
Compensation and benefits	3	2
Fuel	0	0
Materials	2	4
Equipment rents	(3)	0
Depreciation and amortization	0	0
Purchased services and other	(85)	(108)
Total operating expenses	(83)	(102)
Operating income	0	0
Less:
Other expense (income)	0	0
Other components of net periodic benefit recovery cost	0	0
Net interest (income) expense	0	0
(Loss) income before income tax expense and equity in net earnings of subsidiaries	0	0
Income tax expense (recovery)	0	0
Add: Equity in net earnings of subsidiaries	(632)	(552)
Net income	(632)	(552)
Consolidating Adjustments and Eliminations [Member] | Freight
Revenues
Total revenues	0	0
Consolidating Adjustments and Eliminations [Member] | Non-freight
Revenues
Total revenues	(83)	(102)
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member]
Revenues
Total revenues	0	0
Operating expenses
Compensation and benefits	0	0
Fuel	0	0
Materials	0	0
Equipment rents	0	0
Depreciation and amortization	0	0
Purchased services and other	0	0
Total operating expenses	0	0
Operating income	0	0
Less:
Other expense (income)	21	(5)
Other components of net periodic benefit recovery cost	0	0
Net interest (income) expense	0	(1)
(Loss) income before income tax expense and equity in net earnings of subsidiaries	(21)	6
Income tax expense (recovery)	0	0
Add: Equity in net earnings of subsidiaries	430	428
Net income	409	434
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member] | Freight
Revenues
Total revenues	0	0
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member] | Non-freight
Revenues
Total revenues	0	0
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member]
Revenues
Total revenues	1,490	1,273
Operating expenses
Compensation and benefits	275	274
Fuel	167	165
Materials	41	38
Equipment rents	44	33
Depreciation and amortization	115	96
Purchased services and other	243	278
Total operating expenses	885	884
Operating income	605	389
Less:
Other expense (income)	208	(43)
Other components of net periodic benefit recovery cost	(87)	(98)
Net interest (income) expense	122	122
(Loss) income before income tax expense and equity in net earnings of subsidiaries	362	408
Income tax expense (recovery)	134	104
Add: Equity in net earnings of subsidiaries	202	124
Net income	430	428
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member] | Freight
Revenues
Total revenues	1,457	1,244
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member] | Non-freight
Revenues
Total revenues	33	29
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenues
Total revenues	636	596
Operating expenses
Compensation and benefits	120	130
Fuel	45	44
Materials	16	15
Equipment rents	(5)	2
Depreciation and amortization	77	64
Purchased services and other	154	187
Total operating expenses	407	442
Operating income	229	154
Less:
Other expense (income)	(18)	1
Other components of net periodic benefit recovery cost	2	1
Net interest (income) expense	(8)	(7)
(Loss) income before income tax expense and equity in net earnings of subsidiaries	253	159
Income tax expense (recovery)	51	35
Add: Equity in net earnings of subsidiaries	0	0
Net income	202	124
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | Freight
Revenues
Total revenues	543	482
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member] | Non-freight
Revenues
Total revenues	$ 93	$ 114