| Unaudited Interim Condensed Consolidated Statements of Cash Flows Supplemental Information - Summary of Significant Non-Cash Investing and Financing Activities (Detail) - USD ($) $ in Thousands | 3 Months Ended | |
|---|---|---|
| Mar. 31, 2021 | Mar. 31, 2020 | |
| Cash Flow Non Cash Investing And Financing Activities Disclosure [Line Items] | ||
| Share issuance – settlement of outstanding obligations | $ 0 | $ 193 | 
| MPX Warrants [Member] | ||
| Cash Flow Non Cash Investing And Financing Activities Disclosure [Line Items] | ||
| Cashless exercise of MPX warrants recorded as derivatives | $ 0 | $ 3,325 | 
| X | ||||||||||
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- Definition Cash flow non-cash investing and financing activities disclosure [Line item]. No definition available. 
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| X | ||||||||||
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- Definition Non-cash transaction of conversion of warrants or rights as a derivative instrument. No definition available. 
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| X | ||||||||||
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- Definition Noncash investing and financing transaction share issuance settlement of outstanding obligations. No definition available. 
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| X | ||||||||||
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- Details 
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