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Stock-Based Compensation - Summary of Option and RSU Activity (Detail) - Equity Incentive Plan 2019 - $ / shares | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Shares Available for Grant |  |
Balance at the beginning of the year (in shares) | 88,000 | 200,000
Options granted (in shares) |  | (145,000)
Options cancelled and returned to Plan (in shares) |  | 1,000
Plan termination (in shares) |  | (32,000)
Balance at the end of the period (in shares) | 81,000 | 88,000
Number of Shares |  |
Balance at the beginning of the year (in shares) | 161,000 | 17,000
Options granted (in shares) |  | 145,000
Options cancelled and returned to Plan (in shares) | (2,000) | (1,000)
Balance at the end of the period (in shares) | 159,000 | 161,000
Weighted Average Exercise Prices |  |
Weighted-average exercise price (in dollars per share) | $ 10.85 | $ 96.24
Options granted (in dollars per share) |  | 2.64
Options cancelled and returned to Plan (in dollars per share) | 4.00 | 144.00
Weighted-average exercise price (in dollars per share) | $ 10.82 | $ 10.85
Options |  |
Shares Available for Grant |  |
Additional shares authorized under the Plan |  | 183,000
RSU's |  |
Shares Available for Grant |  |
RSUs granted (in shares) | (9,000) | (120,000)
RSUs cancelled and returned to Plan (in shares) | 2,000 | 1,000
Number of Shares |  |
RSUs cancelled and returned to Plan (in shares) | 2,000 | 1,000
Weighted Average Exercise Prices |  |
RSUs granted (in dollars per share) | $ 1.74 | $ 3.79
RSUs cancelled and returned to Plan (in dollars per shares) | $ 4.00 | $ 25.13

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- Definition Represents the rollforward of Shares Available for Grant under the Plans. + References No definition available. + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Number of additional shares authorized for issuance under share-based payment arrangement. + References No definition available. + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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