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Summary of Financial Instruments were Denominated in U S Dollars (Detail)
$ in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2017
CAD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
CAD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
CAD ($)
Disclosure of detailed information about financial instruments [Line Items]              
Cash     $ 65,081   $ 115,705   $ 444,759
Accounts receivable     322,585   293,682    
Accounts payable and accrued liabilities     $ (209,625)   $ (240,736)    
Canadian Operations [Member] | Currency Risk [Member]              
Disclosure of detailed information about financial instruments [Line Items]              
Cash       $ 1,720   $ 37,583  
Accounts payable and accrued liabilities       (13,221)   (20,054)  
Net foreign currency exposure       (11,501)   17,529  
Impact of $0.01 change in the U.S. dollar to Canadian dollar exchange rate on net loss $ (115) $ 175          
Foreign Operations [Member] | Currency Risk [Member]              
Disclosure of detailed information about financial instruments [Line Items]              
Cash       39,636   45,800  
Accounts receivable       152,216   144,302  
Accounts payable and accrued liabilities       (98,008)   (106,635)  
Long-term liabilities, excluding long-term incentive plans       (8,023)   (9,251)  
Net foreign currency exposure       $ 85,821   $ 74,216  
Impact of $0.01 change in the U.S. dollar to Canadian dollar exchange rate on comprehensive loss $ 858 $ 742