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NET INCOME PER COMMON SHARE AND EQUITY PER COMMON SHARE (Details) - $ / shares | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2020
Shares used in computing basic and diluted net income per share [Abstract] |  |  |  |  |
Weighted average common shares outstanding during the period for Basic computation (in shares) | 9,395,000 | 9,326,000 | 9,381,000 | 9,311,000 |
Dilutive effect of employee stock options and awards (in shares) | 30,000 | 41,000 | 35,000 | 46,000 |
Weighted average common shares outstanding during the period for Diluted computation (in shares) | 9,425,000 | 9,367,000 | 9,416,000 | 9,357,000 |
Class A Stock [Member] |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |
Common stock, shares authorized (in shares) | 15,000,000 |  | 15,000,000 |  |
Common stock, shares issued (in shares) | 8,519,129 | 8,451,910 | 8,519,129 | 8,451,910 |
Common stock, shares outstanding (in shares) | 8,519,129 | 8,451,910 | 8,519,129 | 8,451,910 |
Common stock, par value (in dollars per share) | $ 1.00 |  | $ 1.00 |  |
Earnings Per Share [Abstract] |  |  |  |  |
Equity per common share (in dollars per share) |  |  | $ 18.32 |  | $ 18.16
Class B Stock [Member] |  |  |  |  |
Common Stock [Abstract] |  |  |  |  |
Common stock, shares authorized (in shares) | 1,040,000 |  | 1,040,000 |  |
Common stock, shares issued (in shares) | 881,452 | 881,452 | 881,452 | 881,452 |
Common stock, shares outstanding (in shares) | 881,452 | 881,452 | 881,452 | 881,452 |
Common stock, par value (in dollars per share) | $ 1.00 |  | $ 1.00 |  |
Restricted Stock [Member] |  |  |  |  |
Antidilutive Securities Excluded from Computation of Earnings Per Share [Abstract] |  |  |  |  |
Shares excluded from calculations of diluted net income per share (in shares) | 0 | 0 | 0 | 0 |

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- Definition Total number of common shares of an entity that have been sold or granted to shareholders (excludes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding. + References No definition available. + Details
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- Definition The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=125511455&loc=d3e1337-109256 + Details
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