Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Basic net income per share:
Net income applicable to common stockholders	$ 16,239	$ 14,135	$ 23,535	$ 19,870
Undistributed earnings allocated to participating securities	(88)	(112)	(189)	(169)
Net income applicable to common stockholders excluding amounts applicable to participating securities	16,151	14,023	23,346	19,701
Weighted average common shares outstanding	68,938	68,442	68,805	68,419
Basic net income per share	$ 0.23	$ 0.20	$ 0.34	$ 0.29
Diluted net income per share:
Net income applicable to common stockholders	16,239	14,135	23,535	19,870
Undistributed earnings allocated to participating securities	(88)	(112)	(189)	(169)
Net income applicable to common stockholders excluding amounts applicable to participating securities	$ 16,151	$ 14,023	$ 23,346	$ 19,701
Weighted average common shares outstanding	68,938	68,442	68,805	68,419
Dilutive shares from assumed conversion of convertible senior notes	1,877	0	1,734	0
Dilutive stock options and restricted stock	742	416	785	425
Diluted weighted average common shares outstanding	71,557	68,858	71,324	68,844
Diluted net income per share	$ 0.23	$ 0.20	$ 0.33	$ 0.29

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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Amount of undistributed earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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