Condensed Consolidating Financial Information - Interim Condensed Consolidating Statements of Income (Details) - CAD CAD in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Freight	CAD 1,598	CAD 1,406	CAD 3,161	CAD 2,954
Non-freight	45	44	85	87
Total revenues	1,643	1,450	3,246	3,041
Operating expenses
Compensation and benefits	277	284	510	613
Fuel	160	131	330	256
Materials	48	38	97	94
Equipment rents	37	44	73	89
Depreciation and amortization	165	161	331	323
Purchased services and other	277	241	555	462
Total operating expenses	964	899	1,896	1,837
Operating income	679	551	1,350	1,204
Less:
Other income and charges	(61)	(9)	(89)	(190)
Net interest (income) expense	122	115	242	239
Income before income tax expense	618	445	1,197	1,155
Income tax (recovery) expense	138	117	286	287
Add: Equity in net earnings of subsidiaries	0	0	0	0
Net income	480	328	911	868
Consolidating Adjustments and Eliminations [Member]
Revenues
Freight	0	0	0	0
Non-freight	(84)	(87)	(169)	(173)
Total revenues	(84)	(87)	(169)	(173)
Operating expenses
Compensation and benefits	1	1	2	3
Fuel	0	0	0	0
Materials	6	3	12	11
Equipment rents	0	0	0	0
Depreciation and amortization	0	0	0	0
Purchased services and other	(91)	(91)	(183)	(187)
Total operating expenses	(84)	(87)	(169)	(173)
Operating income	0	0	0	0
Less:
Other income and charges	0	0	0	0
Net interest (income) expense	0	0	0	0
Income before income tax expense	0	0	0	0
Income tax (recovery) expense	0	0	0	0
Add: Equity in net earnings of subsidiaries	(591)	(449)	(1,157)	(1,020)
Net income	(591)	(449)	(1,157)	(1,020)
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member]
Revenues
Freight	0	0	0	0
Non-freight	0	0	0	0
Total revenues	0	0	0	0
Operating expenses
Compensation and benefits	0	0	0	0
Fuel	0	0	0	0
Materials	0	0	0	0
Equipment rents	0	0	0	0
Depreciation and amortization	0	0	0	0
Purchased services and other	0	0	0	0
Total operating expenses	0	0	0	0
Operating income	0	0	0	0
Less:
Other income and charges	(5)	(4)	(25)	(73)
Net interest (income) expense	(9)	10	(7)	9
Income before income tax expense	14	(6)	32	64
Income tax (recovery) expense	1	(6)	2	3
Add: Equity in net earnings of subsidiaries	467	328	881	807
Net income	480	328	911	868
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member]
Revenues
Freight	1,129	1,007	2,218	2,104
Non-freight	34	33	66	66
Total revenues	1,163	1,040	2,284	2,170
Operating expenses
Compensation and benefits	165	181	289	382
Fuel	122	103	254	206
Materials	34	27	68	65
Equipment rents	39	53	75	107
Depreciation and amortization	108	107	217	214
Purchased services and other	210	193	418	329
Total operating expenses	678	664	1,321	1,303
Operating income	485	376	963	867
Less:
Other income and charges	(59)	(12)	(66)	(150)
Net interest (income) expense	139	111	264	242
Income before income tax expense	405	277	765	775
Income tax (recovery) expense	62	70	160	181
Add: Equity in net earnings of subsidiaries	124	121	276	213
Net income	467	328	881	807
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenues
Freight	469	399	943	850
Non-freight	95	98	188	194
Total revenues	564	497	1,131	1,044
Operating expenses
Compensation and benefits	111	102	219	228
Fuel	38	28	76	50
Materials	8	8	17	18
Equipment rents	(2)	(9)	(2)	(18)
Depreciation and amortization	57	54	114	109
Purchased services and other	158	139	320	320
Total operating expenses	370	322	744	707
Operating income	194	175	387	337
Less:
Other income and charges	3	7	2	33
Net interest (income) expense	(8)	(6)	(15)	(12)
Income before income tax expense	199	174	400	316
Income tax (recovery) expense	75	53	124	103
Add: Equity in net earnings of subsidiaries	0	0	0	0
Net income	CAD 124	CAD 121	CAD 276	CAD 213