Earnings Per Share - Computation of Basic and Diluted Earnings Per Share for Continuing Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Income from continuing operations	$ 13,121	$ 11,416	$ 48,931	$ 36,442
Basic
Weighted average common shares outstanding	54,594	53,968	54,334	53,632
Diluted
Stock options	1,550	1,544	1,500	1,524
Restricted stock awards	290	319	329	374
Contingent shares	3		3
Diluted weighted average common shares outstanding	56,437	55,831	56,166	55,530
Basic earnings per share from continuing operations	$ 0.24	$ 0.21	$ 0.90	$ 0.68
Diluted earnings per share from continuing operations	$ 0.23	$ 0.20	$ 0.87	$ 0.66

Incremental common shares attributable to restricted stock awards.

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Incremental common shares attributable to stock options.

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Amount after tax of income (loss) from continuing operations attributable to the parent.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

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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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