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Income Taxes - Components of Provision for Income Taxes (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Abstract]      
Current $ (11,997) $ (14,424) $ (10,440)
Deferred (235) (10,044) 27,207
Income tax (expense) recovery $ (12,232) $ (24,468) $ 16,767