Condensed Consolidating Financial Information - Interim Condensed Consolidating Statements of Income (Details) - CAD CAD in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues
Freight	CAD 1,406	CAD 1,610	CAD 2,954	CAD 3,240
Non-freight	44	41	87	76
Total revenues	1,450	1,651	3,041	3,316
Operating expenses
Compensation and benefits	284	308	613	686
Fuel	131	185	256	380
Materials	38	45	94	97
Equipment rents	44	46	89	88
Depreciation and amortization	161	145	323	291
Purchased services and other	241	276	462	516
Total operating expenses	899	1,005	1,837	2,058
Operating income	551	646	1,204	1,258
Less:
Other income and charges	(9)	(5)	(190)	68
Net interest (income) expense	115	84	239	169
Income before income tax expense	445	567	1,155	1,021
Less: Income tax (recovery) expense	117	177	287	311
Add: Equity in net earnings of subsidiaries	0	0	0	0
Net income	328	390	868	710
Consolidating Adjustments and Eliminations [Member]
Revenues
Freight	0	0	0	0
Non-freight	(87)	(83)	(173)	(166)
Total revenues	(87)	(83)	(173)	(166)
Operating expenses
Compensation and benefits	1	0	3	0
Fuel	0	0	0	0
Materials	3	0	11	0
Equipment rents	0	0	0	0
Depreciation and amortization	0	0	0	0
Purchased services and other	(91)	(83)	(187)	(166)
Total operating expenses	(87)	(83)	(173)	(166)
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
Less: Income tax (recovery) expense	0	0	0	0
Add: Equity in net earnings of subsidiaries	(449)	(509)	(1,020)	(1,024)
Net income	(449)	(509)	(1,020)	(1,024)
CPRL (Parent Guarantor) [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	(4)	(3)	(73)	15
Net interest (income) expense	10	0	9	0
Income before income tax expense	(6)	3	64	(15)
Less: Income tax (recovery) expense	(6)	2	3	(2)
Add: Equity in net earnings of subsidiaries	328	389	807	723
Net income	328	390	868	710
CPRC (Subsidiary Issuer) [Member]
Revenues
Freight	1,007	1,131	2,104	2,250
Non-freight	33	34	66	63
Total revenues	1,040	1,165	2,170	2,313
Operating expenses
Compensation and benefits	181	198	382	460
Fuel	103	134	206	295
Materials	27	35	65	78
Equipment rents	53	52	107	88
Depreciation and amortization	107	102	214	204
Purchased services and other	193	192	329	334
Total operating expenses	664	713	1,303	1,459
Operating income	376	452	867	854
Less:
Other income and charges	(12)	(8)	(150)	78
Net interest (income) expense	111	98	242	194
Income before income tax expense	277	362	775	582
Less: Income tax (recovery) expense	70	93	181	160
Add: Equity in net earnings of subsidiaries	121	120	213	301
Net income	328	389	807	723
Non-Guarantor Subsidiaries [Member]
Revenues
Freight	399	479	850	990
Non-freight	98	90	194	179
Total revenues	497	569	1,044	1,169
Operating expenses
Compensation and benefits	102	110	228	226
Fuel	28	51	50	85
Materials	8	10	18	19
Equipment rents	(9)	(6)	(18)	0
Depreciation and amortization	54	43	109	87
Purchased services and other	139	167	320	348
Total operating expenses	322	375	707	765
Operating income	175	194	337	404
Less:
Other income and charges	7	6	33	(25)
Net interest (income) expense	(6)	(14)	(12)	(25)
Income before income tax expense	174	202	316	454
Less: Income tax (recovery) expense	53	82	103	153
Add: Equity in net earnings of subsidiaries	0	0	0	0
Net income	CAD 121	CAD 120	CAD 213	CAD 301