Earnings Per Share (Detail) - shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Weighted average number of shares for calculation of basic EPS – Common Stock	35,920,782	36,720,749	36,448,138
Stock options, restricted stock awards and restricted stock units under equity incentive plans	256,362	92,970	152,665
Weighted average number of shares for calculation of diluted EPS – Common Stock	36,177,144	36,813,719	36,600,803
Stock options outstanding for equity incentive plans
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock that have been excluded from the diluted shares calculation	898,250	2,055,784	1,314,784

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.

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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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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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