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Income Tax - Reconciliation of Income Tax Attributable to Operations (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Income Tax Disclosure [Abstract] |  |  |
Income tax recovery at statutory rates (at a rate of 21% for all years presented) | $ (3,094) | $ (3,490) | $ (2,664)
Expenses not deducted for tax purposes | 118 | 116 | 70
Effect of tax rate changes on deferred tax assets and liabilities | 34 | (13) | (1,416)
Rate differential on foreign earnings | (103) | (296) | (165)
Investment tax credits | (23) | (84) |
Change in valuation allowance | 3,662 | (3,246) | 4,182
Book to tax return adjustments | (518) | (75) | 20
Unrecognized tax benefits |  | 7,192 |
Reversal of previously accrued taxes due to IRS reassessment |  | (221) |
Other | $ (76) | (104) | $ (27)
Income tax expense/(recovery) |  | $ (221) |

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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=120406818&loc=d3e32059-109318 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 + Details
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