Earnings Per Share - Additional Information (Detail) - shares |
12 Months Ended | ||
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Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Earnings Per Share [Line Items] | |||
| Options excluded from the computation of diluted earnings | 116,762 | 346,912 | 0 |
| Class A Common Stock [Member] | |||
| Earnings Per Share [Line Items] | |||
| Common stock, voting rights | One vote per share | ||
| Class B Common Stock [Member] | |||
| Earnings Per Share [Line Items] | |||
| Common stock, voting rights | Ten votes per share | ||
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- Definition Earnings per share disclosure. No definition available.
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- Definition Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Description of voting rights of common stock. Includes eligibility to vote and votes per share owned. Include also, if any, unusual voting rights. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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