Earnings Per Share - Basic and Diluted Weighted Average Shares Outstanding Used to Compute Earnings Per Share (Detail) - shares shares in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share Basic And Diluted [Abstract]
Basic weighted average shares outstanding	37,043	36,954
Dilutive effect of stock options and restricted stock	789	932
Diluted weighted average shares outstanding	37,832	37,886

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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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- Definition

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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