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Equity Compensation Plans - Summary of stock option activity (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Summary Of Stock Option Activity [Abstract] |  |  |
Cash received from options exercised |  | $ 32 | $ 33
Number of shares issuable | 354,268 |  |
Stock based compensation | $ 2,089 | 2,516 | 2,257
Vesting Percentage , Fully Vest , Performace measure | 50.00% |  |
Minimum [Member] |  |  |
Summary Of Stock Option Activity [Abstract] |  |  |
Vesting Percentage , Fully Vest , Performace measure | 50.00% |  |
Maximum [Member] |  |  |
Summary Of Stock Option Activity [Abstract] |  |  |
Vesting Percentage , Pro rata , Performace measure | 50.00% |  |
Employee and Nonemployee Stock Options [Member] |  |  |
Summary Of Stock Option Activity [Abstract] |  |  |
Intrinsic value of options exercised |  | 27 | 27
Cash received from options exercised |  | 32 | 33
Tax benefit realized from option exercises |  | $ 5 | $ 5

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- Definition Percentage of fully earned vesting of award under share-based payment arrangement on the basis of performace measure achieved. + References No definition available. + Details
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- Definition Percentage of pro rata vesting of award under share-based payment arrangement on the basis of performace measure achieved. + References No definition available. + Details
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- Definition Amount of cash inflow from exercise of option under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120381028&loc=SL79508275-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585 + Details
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- Definition Amount of noncash expense for share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + 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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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + 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 (d)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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