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Stockholders' Equity - Additional Information (Detail) - shares | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Jul. 18, 2013
Equity, Class of Treasury Stock [Line Items] |  |  |
Minimum percentage of class A common stock declared dividend excess over class B dividend | 10.00% |  |
Class A Common Stock [Member] |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |
Treasury stock | 3,002,588 |  |
Class B Common Stock [Member] |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |
Minimum percentage of class A common stock declared dividend excess over class B dividend | 10.00% |  |
Treasury stock |  | 72,465 |
Stock Repurchase Program Two [Member] | Class A Common Stock [Member] |  |  |
Equity, Class of Treasury Stock [Line Items] |  |  |
Authority to purchase shares |  |  | 500,000
Common stock shares purchased | 0 | 57,658 |

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