Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

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Amount of decrease of par value, additional paid in capital (APIC) and retained earnings of common and preferred stock retired from treasury when treasury stock is accounted for under the cost method.

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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Number of shares that have been repurchased during the period and are being held in treasury.

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Percentage of board entitled to elect.

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Stockholders Equity Note [Line Items]

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Shareholders' Equity - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 1999
Stockholders Equity Note [Line Items]
Preferred stock outstanding	0	0
Number of shares authorized to be repurchased				7,500,000
Treasury stock, shares repurchased	0	0	0
Cost of repurchased shares	$ 114,425	$ 114,425	$ 114,425
Remaining number of shares authorized to be repurchased	1,129,087
Class B Common Stock
Stockholders Equity Note [Line Items]
Amount of votes common stock is entitled	ten
Treasury stock, shares repurchased	48,263	48,263	48,263
Common Stock
Stockholders Equity Note [Line Items]
Amount of votes common stock is entitled	one
Percentage of Board entitled to elect	25.00%
Treasury stock, shares repurchased	6,322,650	6,322,650	6,322,650