Condensed Consolidating Financial Information - Interim Condensed Consolidating Statements of Comprehensive Income (Details) - CAD CAD in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Net income	CAD 431	CAD 540
Net gain in foreign currency translation adjustments, net of hedging activities	5	37
Change in derivatives designated as cash flow hedges	5	(47)
Change in pension and post-retirement defined benefit plans	38	47
Other comprehensive income before income taxes	48	37
Income tax recovery on above items	(18)	(41)
Equity accounted investments	0	0
Other comprehensive (loss) income	30	(4)
Comprehensive income	461	536
Consolidating Adjustments and Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	(566)	(571)
Net gain in foreign currency translation adjustments, net of hedging activities	0	0
Change in derivatives designated as cash flow hedges	0	0
Change in pension and post-retirement defined benefit plans	0	0
Other comprehensive income before income taxes	0	0
Income tax recovery on above items	0	0
Equity accounted investments	9	275
Other comprehensive (loss) income	9	275
Comprehensive income	(557)	(296)
CPRL (Parent Guarantor) [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	431	540
Net gain in foreign currency translation adjustments, net of hedging activities	0	0
Change in derivatives designated as cash flow hedges	0	0
Change in pension and post-retirement defined benefit plans	0	0
Other comprehensive income before income taxes	0	0
Income tax recovery on above items	0	0
Equity accounted investments	30	(4)
Other comprehensive (loss) income	30	(4)
Comprehensive income	461	536
CPRC (Subsidiary Issuer) [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	414	479
Net gain in foreign currency translation adjustments, net of hedging activities	45	310
Change in derivatives designated as cash flow hedges	5	(47)
Change in pension and post-retirement defined benefit plans	36	45
Other comprehensive income before income taxes	86	308
Income tax recovery on above items	(17)	(41)
Equity accounted investments	(39)	(271)
Other comprehensive (loss) income	30	(4)
Comprehensive income	444	475
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	152	92
Net gain in foreign currency translation adjustments, net of hedging activities	(40)	(273)
Change in derivatives designated as cash flow hedges	0	0
Change in pension and post-retirement defined benefit plans	2	2
Other comprehensive income before income taxes	(38)	(271)
Income tax recovery on above items	(1)	0
Equity accounted investments	0	0
Other comprehensive (loss) income	(39)	(271)
Comprehensive income	CAD 113	CAD (179)