Computation of Earnings Per Share (Detail) - $ / shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share Basic And Diluted [Line Items]
Basic earnings per share, Weighted Average Shares	83,818	84,140	83,807	84,126
Potential dilutive effect of restricted stock units outstanding	35	138	37	146
Diluted earnings per share, Weighted Average Shares	83,853	84,278	83,844	84,272
Basic earnings per share, Earnings per Share	$ 0.44	$ 0.70	$ 0.90	$ 1.33
Potential dilutive effect of restricted stock units outstanding			(0.01)
Diluted earnings per share, Earnings per Share	$ 0.44	$ 0.70	$ 0.89	$ 1.33

Earnings Per Share Basic And Diluted [Line Items]

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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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- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic net Income or Loss per outstanding limited partnership unit in the future and that were not included in the computation of diluted net income per limited partnership unit, because to do so would increase net income per unit amounts or decrease loss per unit amounts for the period presented.

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- Definition

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

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The amount of net income (loss) for 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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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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