XML 137 R100.htm IDEA: XBRL DOCUMENT v3.19.1
Income taxes - Summary of Temporary Difference (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets $ 84,043 $ 58,144
Deferred tax liabilities 513,972 607,270
Expense (recovery) (118,839) (19,849)
Property, plant and equipment [member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities 483,561 592,062
Expense (recovery) (108,501) (33,466)
Loss carryforwards [member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 37,245 31,457
Expense (recovery) (5,788) (4,641)
Liabilities [member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 27,321 24,690
Expense (recovery) (2,631) (80)
Investment tax credits [member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax liabilities 20,000 0
Expense (recovery) 20,000 0
Other items [member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Deferred tax assets 19,477 1,997
Deferred tax liabilities 10,411 15,208
Expense (recovery) $ (21,919) $ 18,338