Income Tax Expense (Recovery) - Components of Provision for Income Tax (Expense) Recovery (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Current	$ 16,408	$ (3,219)	$ 12,622	$ (8,072)
Deferred	767	(185)	761	(368)
Income tax recovery (expense)	$ 17,175	$ (3,404)	$ 13,383	$ (8,440)

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration