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Stockholders' Equity (Narrative) (Details) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Mar. 31, 2020 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Sep. 30, 2020 | Sep. 30, 2019 | Nov. 06, 2019
Class of Stock [Line Items] |  |  |  |  |  |  |
Common stock repurchased | $ 1,002,000 | $ 25,000 | $ 85,000 | $ 1,300,000 |  |  |
2019 Stock Repurchase Program |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Stock repurchase program, authorized amount |  |  |  |  |  |  | $ 25,000,000
Class A Common Stock | 2019 Stock Repurchase Program |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Common stock repurchased (in shares) |  |  |  |  | 32,286 |  |
Common stock repurchased |  |  |  |  | $ 1,000,000.0 |  |
Class A Common Stock | 2018 Stock Repurchase Program |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |
Common stock repurchased (in shares) |  | 525 |  |  |  | 39,049 |
Common stock repurchased |  | $ 100,000 |  |  |  | $ 1,400,000 |

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