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Stock-Based Compensation And Stock Repurchases (Narrative) (Details) - USD ($) |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |
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Aug. 11, 2021 | Dec. 16, 2020 | Dec. 16, 2020 | Mar. 10, 2020 | Mar. 05, 2020 | May 07, 2019 | Apr. 30, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020 | Mar. 02, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Stock Options, Granted |  |  |  |  |  |  |  |  |  | 0 |  |  |
Stock Option [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Compensation expense |  |  |  |  |  |  |  | $ 101,000 | $ 103,000 | $ 302,000 | $ 343,000 |  |
Unrecognized estimated compensation cost related to non-vested stock options granted |  |  |  |  |  |  |  | 300,000 |  | $ 300,000 |  |  |
Recognition period of unrecognized compensation cost |  |  |  |  |  |  |  |  |  | 1 year 21 days |  |  |
Share price |  |  |  |  |  |  |  |  |  | $ 5.06 |  |  |
Intrinsic unrealized value of all options outstanding, vested and expected to vest |  |  |  |  |  |  |  |  |  |  |  |  |
2020 Stock Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Terms of award |  |  |  |  |  |  |  |  |  | the grantee to receive one share for every RSU based on a vesting plan |  |  |
Minimum [Member] | 2020 Stock Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 1 year |  |  |
Maximum [Member] | 2020 Stock Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 4 years |  |  |
Stock option expiry period |  |  |  |  |  |  |  |  |  | 5 years |  |  |
Class A [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock authorized for issuance |  |  |  |  |  |  |  | 1,505,598 |  | 1,505,598 |  |  |
Shares repurchased plan, shares |  |  |  |  |  |  |  |  |  | 0 |  |  |
Number of Stock Options, Granted |  |  |  |  |  |  |  |  |  |  |  | 38,803 |
Class A [Member] | 2020 Stock Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Common Stock authorized for issuance |  |  |  |  |  |  |  | 1,250,000 |  | 1,250,000 |  |  |
Common Stock shares remaining for future issuances |  |  |  |  |  |  |  | 784,296 |  | 784,296 |  |  |
Class A [Member] | Maximum [Member] | 2020 Stock Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Additional shares authorized |  |  |  |  |  |  |  |  |  | 176,086 |  |  |
2017 Stock Repurchase Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase program, amount authorized |  |  |  | $ 25,000,000.0 |  |  |  |  |  |  |  |  |
Repurchase program, remaining amount authorized |  |  |  |  |  |  |  | $ 26,000,000.0 |  | $ 26,000,000.0 |  |  |
Stock buy-back program period |  |  |  |  |  |  |  |  |  | 2 years |  |  |
2017 Stock Repurchase Plan [Member] | Class A [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase program, amount authorized |  |  |  |  |  |  |  |  |  |  |  |  | $ 25,000,000.0
Repurchase program, remaining amount authorized |  |  |  | $ 26,000,000.0 |  |  |  |  |  |  |  |  |
$25 Million Stock Repurchase Program [Member] | Class A Nonvoting Common Stock [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase value |  |  |  |  |  |  |  | 24,000,000.0 |  | $ 24,000,000.0 |  |  |
Share price |  |  |  |  | $ 7.30 |  |  |  |  | $ 13.39 |  |  |
Shares repurchased plan, shares |  |  |  |  | 25,000 |  |  |  |  | 1,792,819 |  |  |
Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Compensation expense |  |  |  |  |  | $ 35,000 |  | 505,000 | $ 237,000 | $ 1,290,000 | $ 708,000 |  |
Unrecognized estimated compensation cost related to non-vested stock options granted |  |  |  |  |  |  |  | $ 3,300,000 |  | $ 3,300,000 |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 1 year 9 months 21 days |  |  |
Executive Officer [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Number of options, Granted |  |  |  |  |  |  | 262,830 |  |  |  |  |  |
Executive Officer [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 4 years |  |  |
Percentage of shares vested |  |  |  |  |  |  |  |  |  | 50.00% |  |  |
Percentage of RSUs Vesting Period Contingent On Performance Metrics |  |  |  |  |  |  |  |  |  | 50.00% |  |  |
Management [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 4 years |  |  |
Percentage of shares vested |  |  |  |  |  |  |  |  |  | 25.00% |  |  |
Non-employee Director [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Stock Options, Granted |  |  | 38,803 |  |  |  |  |  |  |  |  |  |
Non-employee Director [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of shares vested |  |  |  |  |  |  |  |  |  | 100.00% |  |  |
Number of options, Granted | 26,924 |  | 60,084 |  |  |  |  |  |  |  |  |  |
Executive Management And Other Employees [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 1 year |  |  |
Percentage of shares vested |  |  |  |  |  |  |  |  |  | 100.00% |  |  |
Number of options, Granted |  | 114,803 |  | 287,163 |  |  |  |  |  |  |  |  |
Other employees [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Vesting period of stock options and RSU |  |  |  |  |  |  |  |  |  | 4 years |  |  |
Percentage of shares vested |  |  |  |  |  |  |  |  |  | 25.00% |  |  |
Number of options, Granted |  |  |  |  |  |  |  |  |  | 22,888 |  |  |

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