Miscellaneous Financial Information - Additional Information (Detail) (CAD) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Additional Financial Information [Line Items]
Effect of LIFO inventory liquidation on income	29	24	45
Difference between LIFO carrying values and replacement cost of inventories	857	1,787
Research and development costs charged to expenses	128us-gaap_ResearchAndDevelopmentExpense	154us-gaap_ResearchAndDevelopmentExpense	147us-gaap_ResearchAndDevelopmentExpense
Accounts payable and accrued liabilities included accrued taxes other than income taxes	408	380

Carrying value as of the balance sheet date of obligations incurred and payable for real and property taxes.

The effect of liquidating LIFO (last in first out) inventory layers on income.

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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