Condensed Consolidating Financial Information - Condensed Consolidating Balance Sheets (Detail) - CAD CAD in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	CAD 650	CAD 226	CAD 476	CAD 333
Accounts receivable, net	645	702
Accounts receivable, inter-company	0	0
Short-term advances to affiliates	0	0
Materials and supplies	188	177
Other current assets	54	116
Total current assets	1,537	1,221
Long-term advances to affiliates	0	0
Investments	152	112
Investments in subsidiaries	0	0
Properties	16,273	14,438
Assets held for sale	0	182
Goodwill and intangible assets	211	176	162
Pension asset	1,401	304
Other assets	63	117
Deferred income taxes	0	0
Total assets	19,637	16,550
Current liabilities
Accounts payable and accrued liabilities	1,417	1,277
Accounts payable, inter-company	0	0
Short-term advances from affiliates	0	0
Long-term debt maturing within one year	30	134
Total current liabilities	1,447	1,411
Pension and other benefit liabilities	758	755
Long-term advances from affiliates	0	0
Other long-term liabilities	318	432
Long-term debt	8,927	5,625
Deferred income taxes	3,391	2,717
Total liabilities	14,841	10,940
Shareholders’ equity
Share capital	2,058	2,185
Additional paid-in capital	43	36
Accumulated other comprehensive (loss) income	(1,477)	(2,219)
Retained earnings	4,172	5,608
Total Shareholders' equity	4,796	5,610	7,097	5,097
Total liabilities and shareholders’ equity	19,637	16,550
Consolidating Adjustments and Eliminations [Member]
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Accounts receivable, inter-company	(429)	(435)
Short-term advances to affiliates	(3,558)	(2,144)
Materials and supplies	0	0
Other current assets	0	0
Total current assets	(3,987)	(2,579)
Long-term advances to affiliates	(1,084)	(1,524)
Investments	0	0
Investments in subsidiaries	(17,350)	(15,849)
Properties	0	0
Assets held for sale		0
Goodwill and intangible assets	0	0
Pension asset	0	0
Other assets	0	0
Deferred income taxes	25	56
Total assets	(22,446)	(20,008)
Current liabilities
Accounts payable and accrued liabilities	0	0
Accounts payable, inter-company	(429)	(435)
Short-term advances from affiliates	(3,558)	(2,144)
Long-term debt maturing within one year	0	0
Total current liabilities	(3,987)	(2,579)
Pension and other benefit liabilities	0	0
Long-term advances from affiliates	(1,084)	(1,524)
Other long-term liabilities	0	0
Long-term debt	0	0
Deferred income taxes	(25)	(56)
Total liabilities	(5,096)	(4,159)
Shareholders’ equity
Share capital	(6,502)	(6,159)
Additional paid-in capital	(2,181)	(2,116)
Accumulated other comprehensive (loss) income	637	2,049
Retained earnings	(9,304)	(9,623)
Total Shareholders' equity	(17,350)	(15,849)
Total liabilities and shareholders’ equity	(22,446)	(20,008)
CPRL (Parent Guarantor) [Member]
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Accounts receivable, inter-company	59	58
Short-term advances to affiliates	0	0
Materials and supplies	0	0
Other current assets	0	0
Total current assets	59	58
Long-term advances to affiliates	501	1
Investments	0	0
Investments in subsidiaries	7,518	7,618
Properties	0	0
Assets held for sale		0
Goodwill and intangible assets	0	0
Pension asset	0	0
Other assets	0	0
Deferred income taxes	(25)	(4)
Total assets	8,103	7,681
Current liabilities
Accounts payable and accrued liabilities	54	97
Accounts payable, inter-company	0	0
Short-term advances from affiliates	3,253	1,974
Long-term debt maturing within one year	0	0
Total current liabilities	3,307	2,071
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	3,307	2,071
Shareholders’ equity
Share capital	2,058	2,185
Additional paid-in capital	43	36
Accumulated other comprehensive (loss) income	(1,477)	(2,219)
Retained earnings	4,172	5,608
Total Shareholders' equity	4,796	5,610
Total liabilities and shareholders’ equity	8,103	7,681
CPRC (Subsidiary Issuer) [Member]
Current assets
Cash and cash equivalents	502	152	91	211
Accounts receivable, net	452	490
Accounts receivable, inter-company	105	147
Short-term advances to affiliates	75	170
Materials and supplies	154	137
Other current assets	37	27
Total current assets	1,325	1,123
Long-term advances to affiliates	207	207
Investments	22	15
Investments in subsidiaries	9,832	8,231
Properties	8,481	7,976
Assets held for sale		8
Goodwill and intangible assets	3	0
Pension asset	1,401	304
Other assets	55	94
Deferred income taxes	0	(15)
Total assets	21,326	17,973
Current liabilities
Accounts payable and accrued liabilities	1,122	896
Accounts payable, inter-company	325	288
Short-term advances from affiliates	230	0
Long-term debt maturing within one year	24	91
Total current liabilities	1,701	1,275
Pension and other benefit liabilities	676	692
Long-term advances from affiliates	877	1,316
Other long-term liabilities	186	286
Long-term debt	8,863	5,570
Deferred income taxes	1,505	1,216
Total liabilities	13,808	10,355
Shareholders’ equity
Share capital	1,037	1,037
Additional paid-in capital	1,568	1,547
Accumulated other comprehensive (loss) income	(1,477)	(2,219)
Retained earnings	6,390	7,253
Total Shareholders' equity	7,518	7,618
Total liabilities and shareholders’ equity	21,326	17,973
Non-Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents	148	74	CAD 385	CAD 122
Accounts receivable, net	193	212
Accounts receivable, inter-company	265	230
Short-term advances to affiliates	3,483	1,974
Materials and supplies	34	40
Other current assets	17	89
Total current assets	4,140	2,619
Long-term advances to affiliates	376	1,316
Investments	130	97
Investments in subsidiaries	0	0
Properties	7,792	6,462
Assets held for sale		174
Goodwill and intangible assets	208	176
Pension asset	0	0
Other assets	8	23
Deferred income taxes	0	(37)
Total assets	12,654	10,904
Current liabilities
Accounts payable and accrued liabilities	241	284
Accounts payable, inter-company	104	147
Short-term advances from affiliates	75	170
Long-term debt maturing within one year	6	43
Total current liabilities	426	644
Pension and other benefit liabilities	82	63
Long-term advances from affiliates	207	208
Other long-term liabilities	132	146
Long-term debt	64	55
Deferred income taxes	1,911	1,557
Total liabilities	2,822	2,673
Shareholders’ equity
Share capital	5,465	5,122
Additional paid-in capital	613	569
Accumulated other comprehensive (loss) income	840	170
Retained earnings	2,914	2,370
Total Shareholders' equity	9,832	8,231
Total liabilities and shareholders’ equity	CAD 12,654	CAD 10,904