Calculation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Basic net income per share:
Net income applicable to common stockholders	$ 27,524	$ 10,474
Weighted average common shares outstanding	65,037	68,731
Basic net income per share	$ 0.42	$ 0.15
Diluted net income per share:
Net income applicable to common stockholders	$ 27,524	$ 10,474
Weighted average common shares outstanding	65,037	68,731
Dilutive shares from assumed conversion of convertible senior notes	0	1,729
Dilutive stock options and restricted stock	1,187	1,095
Diluted weighted average common shares outstanding	66,224	71,555
Diluted net income per share	$ 0.42	$ 0.15

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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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of convertible debt securities using the if-converted method.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the 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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