Condensed Consolidating Financial Information - Interim Condensed Consolidating Statements of Income (Details) - CAD CAD in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues
Freight	CAD 1,510	CAD 1,667	CAD 4,464	CAD 4,907
Non-freight	44	42	131	118
Total revenues	1,554	1,709	4,595	5,025
Operating expenses
Compensation and benefits	294	352	907	1,038
Fuel	138	162	394	542
Materials	39	47	133	144
Equipment rents	43	42	132	130
Depreciation and amortization	155	149	478	440
Purchased services and other	228	272	690	788
Gain (Loss) on Disposition of Property Plant Equipment	0	(68)		(68)
Total operating expenses	897	956	2,734	3,014
Operating income	657	753	1,861	2,011
Less:
Other income and charges	71	168	(119)	236
Net interest (income) expense	116	103	355	272
Income before income tax expense	470	482	1,625	1,503
Less: Income tax (recovery) expense	123	159	410	470
Add: Equity in net earnings of subsidiaries	0	0	0	0
Net income	347	323	1,215	1,033
Consolidating Adjustments and Eliminations [Member]
Revenues
Freight	0	0	0	0
Non-freight	(86)	(82)	(259)	(248)
Total revenues	(86)	(82)	(259)	(248)
Operating expenses
Compensation and benefits	2	0	5	0
Fuel	0	0	0	0
Materials	3	0	14	0
Equipment rents	0	0	0	0
Depreciation and amortization	0	0	0	0
Purchased services and other	(91)	(82)	(278)	(248)
Gain (Loss) on Disposition of Property Plant Equipment		0		0
Total operating expenses	(86)	(82)	(259)	(248)
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	(512)	(597)	(1,532)	(1,621)
Net income	(512)	(597)	(1,532)	(1,621)
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
Gain (Loss) on Disposition of Property Plant Equipment		0		0
Total operating expenses	0	0	0	0
Operating income	0	0	0	0
Less:
Other income and charges	12	29	(61)	44
Net interest (income) expense	(9)	(3)	0	(3)
Income before income tax expense	(3)	(26)	61	(41)
Less: Income tax (recovery) expense	9	(4)	12	(6)
Add: Equity in net earnings of subsidiaries	359	345	1,166	1,068
Net income	347	323	1,215	1,033
CPRC (Subsidiary Issuer) [Member]
Revenues
Freight	1,078	1,127	3,182	3,377
Non-freight	35	33	101	96
Total revenues	1,113	1,160	3,283	3,473
Operating expenses
Compensation and benefits	181	251	563	711
Fuel	111	122	317	417
Materials	30	38	95	116
Equipment rents	48	44	155	132
Depreciation and amortization	102	102	316	306
Purchased services and other	170	179	499	513
Gain (Loss) on Disposition of Property Plant Equipment		0		0
Total operating expenses	642	736	1,945	2,195
Operating income	471	424	1,338	1,278
Less:
Other income and charges	61	162	(89)	240
Net interest (income) expense	131	119	373	313
Income before income tax expense	279	143	1,054	725
Less: Income tax (recovery) expense	73	50	254	210
Add: Equity in net earnings of subsidiaries	153	252	366	553
Net income	359	345	1,166	1,068
Non-Guarantor Subsidiaries [Member]
Revenues
Freight	432	540	1,282	1,530
Non-freight	95	91	289	270
Total revenues	527	631	1,571	1,800
Operating expenses
Compensation and benefits	111	101	339	327
Fuel	27	40	77	125
Materials	6	9	24	28
Equipment rents	(5)	(2)	(23)	(2)
Depreciation and amortization	53	47	162	134
Purchased services and other	149	175	469	523
Gain (Loss) on Disposition of Property Plant Equipment		(68)		(68)
Total operating expenses	341	302	1,048	1,067
Operating income	186	329	523	733
Less:
Other income and charges	(2)	(23)	31	(48)
Net interest (income) expense	(6)	(13)	(18)	(38)
Income before income tax expense	194	365	510	819
Less: Income tax (recovery) expense	41	113	144	266
Add: Equity in net earnings of subsidiaries	0	0	0	0
Net income	CAD 153	CAD 252	CAD 366	CAD 553