Components of Deferred Income Tax Liabilities and Assets (Detail) (CAD) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components Of Deferred Tax Assets And Liabilities [Line Items]
Depreciation and amortization	2,949	2,434	1,948
Successful drilling and land acquisitions	815	399	378
Pension and benefits	(376)	(717)	(720)
Site restoration	(287)	(284)	(267)
Capitalized interest	69	53	50
Other	(99)	39	51
Net long-term deferred income tax liabilities	3,071	1,924	1,440
LIFO inventory valuation	(450)	(478)	(560)
Other	(109)	(49)	(30)
Net current deferred income tax assets	(559)	(527)	(590)
Valuation allowance
Net deferred income tax liabilities	2,512	1,397	850