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Derivative Financial Instruments - Additional Information (Detail) - 12 months ended Dec. 31, 2016
CAD in Millions, $ in Millions
CAD
USD ($)
Disclosure of detailed information about financial instruments [line items]    
Realized loss on cash flow hedge CAD (10.2)  
Forward contract [member]    
Disclosure of detailed information about financial instruments [line items]    
Foreign currency forward contract agreements value | $   $ 773.0
Value of foreign currency forward contract purchased 1,009.0  
Realized loss on cash flow hedge CAD (10.2)  
Forward contract [member] | Top of range [member]    
Disclosure of detailed information about financial instruments [line items]    
Derivative fixed rate 1.3236  
Forward contract [member] | Bottom of range [member]    
Disclosure of detailed information about financial instruments [line items]    
Derivative fixed rate 1.28655