Annual report pursuant to Section 13 and 15(d)

Income Tax - Summary of Investment Tax Credits and Non-Capital Losses and Net Operating Losses (Detail)

v3.8.0.1
Income Tax - Summary of Investment Tax Credits and Non-Capital Losses and Net Operating Losses (Detail) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses $ 9,900 $ 1,300
UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 849 200
US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 9,874  
Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 2,603  
Investment tax credits carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 2,600 2,600
Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 120,400 $ 115,900
Non-capital Losses 120,423  
2026 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 244  
2026 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 7,335  
2027 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 71  
2027 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 4,949  
2028 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 148  
2028 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 8,020  
2029 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 35  
2029 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 9  
2029 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 317  
2029 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses (9)  
2030 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 21  
2030 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 5  
2030 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 346  
2030 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 6,288  
2031 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 37  
2031 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 17  
2031 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 486  
2031 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 12,121  
2032 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 43  
2032 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 43  
2032 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 363  
2032 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 17,278  
2033 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 56  
2033 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 2  
2033 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 193  
2033 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 23,240  
2034 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 48  
2034 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 3  
2034 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 215  
2034 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 17,077  
2035 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 28  
2035 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 654  
2035 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 122  
2035 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 3,112  
2036 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 3  
2036 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 611  
2036 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 79  
2036 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses 16,664  
2037 [Member] | UNITED KINGDOM    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 578  
2037 [Member] | US [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Net Operating Losses 8,530  
2037 [Member] | Investment tax credits carryforwards [Member]    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Investment tax credits 19  
2037 [Member] | Non Capital Loss Carryforwards [Member] | CANADA    
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]    
Non-capital Losses $ 4,348