Pensions and Other Benefits - Summary of Defined Benefit Pension Plan Assets Measured at Fair Value Using Unobservable Inputs (Detail) - Real Estate [Member] - Defined Benefit Plan - CAD CAD in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Beginning Balance	CAD 654	CAD 847
Disbursements	(223)	(236)
Net realized gains	64	67
Increase (decrease) in net unrealized gains	(44)	(24)
Ending Balance	CAD 451	CAD 654