Income Tax - Summary of Investment Tax Credits and Non-Capital Losses and Net Operating Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	$ 25,300	$ 17,600
Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	104,213
UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	2,691	1,800
US [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	25,291
Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	2,973
Investment tax credits carryforwards [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	2,900	$ 2,600
2022 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	1
2025 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	244
2026 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	7,660
2026 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	71
2027 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	6,082
2028 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	7,256
2028 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	111
2029 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	1,712
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
2030 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	6,770
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
2031 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	12,354
2031 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	36
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
2032 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	17,278
2032 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	42
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
2033 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	23,240
2033 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	54
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
2034 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	17,077
2034 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	46
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
2035 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	3,112
2035 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	27
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
2036 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	5,361
2036 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	58
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
2037 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	(5,295)
2037 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	493
2037 [Member] | US [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	8,763
2037 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	22
2038 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	(3,179)
2038 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	887
2038 [Member] | US [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	7,207
2038 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	202
2039 [Member] | Canada
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Non-capital Losses	4,785
2039 [Member] | UK
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	1,048
2039 [Member] | US [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Net Operating Losses	7,977
2039 [Member] | Investment tax credits carryforwards [Member]
Schedule Of Tax Credits And Losses Carry Forward Expiration [Line Items]
Investment Tax Credits	$ 201