Stockholders' Equity - Summary of Shares Issued and Held in Treasury or Outstanding (Detail) - shares	Jun. 30, 2020	Dec. 31, 2019
Class A Common Stock [Member]
Class of Stock [Line Items]
Common stock - issued	17,205,821	17,136,493
Common stock - held in treasury	(1,987,520)	(1,692,059)
Common stock - outstanding	15,218,301	15,444,434
Class B Common Stock [Member]
Class of Stock [Line Items]
Common stock - issued	234,903	234,903
Common stock - held in treasury	(234,903)	(234,903)
Common stock - outstanding	0	0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes 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 and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

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-Publisher FASB
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-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
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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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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Publisher FASB
-Name Accounting Standards Codification
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