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Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Details) - Recurring [Member] - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Marketable Equity Security [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | $ 10 | $ 11
Equity Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 5,621 | 3,764
U.S. Treasury Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 8,915 | 12,506
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Marketable Equity Security [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 10 | 11
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 0 | 0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 8,915 | 12,506
Significant Other Observable Inputs (Level 2) [Member] | Marketable Equity Security [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 0 | 0
Significant Other Observable Inputs (Level 2) [Member] | Equity Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 5,621 | 3,764
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Marketable Equity Security [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | Equity Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | 0 | 0
Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury Mutual Fund [Member] |  |
Fair Value Assets Measured On Recurring Basis [Line Items] |  |
Fair value assets | $ 0 | $ 0

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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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