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Equity Plans - Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Compensation costs charged to income: | $ 3,553 | $ 3,406 | $ 2,117
Proceeds from the exercise of stock options and similar instruments: | 1,830 | 1,603 | 1,371
Restricted Stock and Deferred Restricted Stock |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Compensation costs charged to income: | 3,230 | 3,123 | 1,875
Employee Stock Purchase Plan |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Compensation costs charged to income: | 323 | 283 | 242
Proceeds from the exercise of stock options and similar instruments: | $ 1,830 | $ 1,603 | $ 1,371

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- Definition Amount of cash inflow from issuance of shares under share-based payment arrangement. Includes, but is not limited to, option exercised. + 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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