Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheets (Detail) - CAD CAD in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets
Cash and cash equivalents	CAD 164	CAD 650
Accounts receivable, net	591	645
Accounts receivable, intercompany	0	0
Short-term advances to affiliates	0	0
Materials and supplies	184	188
Other current assets	70	54
Total current assets	1,009	1,537
Long-term advances to affiliates	0	0
Investments	194	152
Investments in subsidiaries	0	0
Properties	16,689	16,273
Goodwill and intangible assets	202	211	CAD 176
Pension asset	1,070	1,401
Other assets	57	63
Deferred income taxes	0	0
Total assets	19,221	19,637
Current liabilities
Accounts payable and accrued liabilities	1,322	1,417
Accounts payable, inter-company	0	0
Short-term advances from affiliates	0	0
Long-term debt maturing within one year	25	30
Total current liabilities	1,347	1,447
Pension and other benefit liabilities	734	758
Long-term advances from affiliates	0	0
Other long-term liabilities	284	318
Long-term debt	8,659	8,927
Deferred income taxes	3,571	3,391
Total liabilities	14,595	14,841
Shareholders’ equity
Share capital	2,002	2,058
Accumulated other comprehensive loss (Note 7)	52	43
Accumulated other comprehensive (loss) income	(1,799)	(1,477)
Retained earnings	4,371	4,172
Total Shareholders' equity	4,626	4,796	CAD 5,610	CAD 7,097
Total liabilities and shareholders’ equity	19,221	19,637
Consolidating Adjustments and Eliminations [Member]
Current assets
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Accounts receivable, intercompany	(409)	(429)
Short-term advances to affiliates	(5,227)	(3,558)
Materials and supplies	0	0
Other current assets	0	0
Total current assets	(5,636)	(3,987)
Long-term advances to affiliates	(92)	(1,084)
Investments	0	0
Investments in subsidiaries	(18,762)	(17,350)
Properties	0	0
Goodwill and intangible assets	0	0
Pension asset	0	0
Other assets	0	0
Deferred income taxes	(11)	(25)
Total assets	(24,501)	(22,446)
Current liabilities
Accounts payable and accrued liabilities	0	0
Accounts payable, inter-company	(409)	(429)
Short-term advances from affiliates	(5,227)	(3,558)
Long-term debt maturing within one year	0	0
Total current liabilities	(5,636)	(3,987)
Pension and other benefit liabilities	0	0
Long-term advances from affiliates	(92)	(1,084)
Other long-term liabilities	0	0
Long-term debt	0	0
Deferred income taxes	(11)	(25)
Total liabilities	(5,739)	(5,096)
Shareholders’ equity
Share capital	(6,860)	(6,502)
Accumulated other comprehensive loss (Note 7)	(1,936)	(2,181)
Accumulated other comprehensive (loss) income	1,087	637
Retained earnings	(11,053)	(9,304)
Total Shareholders' equity	(18,762)	(17,350)
Total liabilities and shareholders’ equity	(24,501)	(22,446)
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member]
Current assets
Cash and cash equivalents	0	0
Accounts receivable, net	0	0
Accounts receivable, intercompany	90	59
Short-term advances to affiliates	500	0
Materials and supplies	0	0
Other current assets	0	0
Total current assets	590	59
Long-term advances to affiliates	1	501
Investments	0	0
Investments in subsidiaries	8,513	7,518
Properties	0	0
Goodwill and intangible assets	0	0
Pension asset	0	0
Other assets	1	0
Deferred income taxes	11	25
Total assets	9,116	8,103
Current liabilities
Accounts payable and accrued liabilities	73	54
Accounts payable, inter-company	14	0
Short-term advances from affiliates	4,403	3,253
Long-term debt maturing within one year	0	0
Total current liabilities	4,490	3,307
Pension and other benefit liabilities	0	0
Long-term advances from affiliates	0	0
Other long-term liabilities	0	0
Long-term debt	0	0
Deferred income taxes	0	0
Total liabilities	4,490	3,307
Shareholders’ equity
Share capital	2,002	2,058
Accumulated other comprehensive loss (Note 7)	52	43
Accumulated other comprehensive (loss) income	(1,799)	(1,477)
Retained earnings	4,371	4,172
Total Shareholders' equity	4,626	4,796
Total liabilities and shareholders’ equity	9,116	8,103
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member]
Current assets
Cash and cash equivalents	100	502
Accounts receivable, net	435	452
Accounts receivable, intercompany	113	105
Short-term advances to affiliates	692	75
Materials and supplies	150	154
Other current assets	38	37
Total current assets	1,528	1,325
Long-term advances to affiliates	0	207
Investments	47	22
Investments in subsidiaries	10,249	9,832
Properties	8,756	8,481
Goodwill and intangible assets	0	3
Pension asset	1,070	1,401
Other assets	48	55
Deferred income taxes	0	0
Total assets	21,698	21,326
Current liabilities
Accounts payable and accrued liabilities	945	1,122
Accounts payable, inter-company	292	325
Short-term advances from affiliates	816	230
Long-term debt maturing within one year	25	24
Total current liabilities	2,078	1,701
Pension and other benefit liabilities	658	676
Long-term advances from affiliates	92	877
Other long-term liabilities	152	186
Long-term debt	8,605	8,863
Deferred income taxes	1,600	1,505
Total liabilities	13,185	13,808
Shareholders’ equity
Share capital	1,037	1,037
Accumulated other comprehensive loss (Note 7)	1,638	1,568
Accumulated other comprehensive (loss) income	(1,799)	(1,477)
Retained earnings	7,637	6,390
Total Shareholders' equity	8,513	7,518
Total liabilities and shareholders’ equity	21,698	21,326
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Current assets
Cash and cash equivalents	64	148
Accounts receivable, net	156	193
Accounts receivable, intercompany	206	265
Short-term advances to affiliates	4,035	3,483
Materials and supplies	34	34
Other current assets	32	17
Total current assets	4,527	4,140
Long-term advances to affiliates	91	376
Investments	147	130
Investments in subsidiaries	0	0
Properties	7,933	7,792
Goodwill and intangible assets	202	208
Pension asset	0	0
Other assets	8	8
Deferred income taxes	0	0
Total assets	12,908	12,654
Current liabilities
Accounts payable and accrued liabilities	304	241
Accounts payable, inter-company	103	104
Short-term advances from affiliates	8	75
Long-term debt maturing within one year	0	6
Total current liabilities	415	426
Pension and other benefit liabilities	76	82
Long-term advances from affiliates	0	207
Other long-term liabilities	132	132
Long-term debt	54	64
Deferred income taxes	1,982	1,911
Total liabilities	2,659	2,822
Shareholders’ equity
Share capital	5,823	5,465
Accumulated other comprehensive loss (Note 7)	298	613
Accumulated other comprehensive (loss) income	712	840
Retained earnings	3,416	2,914
Total Shareholders' equity	10,249	9,832
Total liabilities and shareholders’ equity	CAD 12,908	CAD 12,654