Condensed Consolidating Financial Information - Interim Condensed Consolidating Statements of Comprehensive Income (Details) - CAD CAD in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	CAD 540	CAD 320
Net gain (loss) in foreign currency translation adjustments, net of hedging activities	37	(37)
Change in derivatives designated as cash flow hedges	(47)	(69)
Change in pension and post-retirement defined benefit plans	47	72
Other comprehensive income (loss) before income taxes	37	(34)
Income tax recovery (expense) on above items	(41)	46
Equity accounted investments	0	0
Other comprehensive (loss) income	(4)	12
Comprehensive income	536	332
Consolidating Adjustments and Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	(571)	(515)
Net gain (loss) 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 (loss) before income taxes	0	0
Income tax recovery (expense) on above items	0	0
Equity accounted investments	275	(312)
Other comprehensive (loss) income	275	(312)
Comprehensive income	(296)	(827)
CPRL (Parent Guarantor) [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	540	320
Net gain (loss) 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 (loss) before income taxes	0	0
Income tax recovery (expense) on above items	0	0
Equity accounted investments	(4)	12
Other comprehensive (loss) income	(4)	12
Comprehensive income	536	332
CPRC (Subsidiary Issuer) [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	479	334
Net gain (loss) in foreign currency translation adjustments, net of hedging activities	310	(357)
Change in derivatives designated as cash flow hedges	(47)	(69)
Change in pension and post-retirement defined benefit plans	45	70
Other comprehensive income (loss) before income taxes	308	(356)
Income tax recovery (expense) on above items	(41)	68
Equity accounted investments	(271)	300
Other comprehensive (loss) income	(4)	12
Comprehensive income	475	346
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income	92	181
Net gain (loss) in foreign currency translation adjustments, net of hedging activities	(273)	320
Change in derivatives designated as cash flow hedges	0	0
Change in pension and post-retirement defined benefit plans	2	2
Other comprehensive income (loss) before income taxes	(271)	322
Income tax recovery (expense) on above items	0	(22)
Equity accounted investments	0	0
Other comprehensive (loss) income	(271)	300
Comprehensive income	CAD (179)	CAD 481