Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Basic net income per share:
Net income applicable to common stockholders	$ 18,307	$ 16,236	$ 41,842	$ 36,106
Undistributed earnings allocated to participating securities	(103)	(117)	(340)	(293)
Net income applicable to common stockholders excluding amounts applicable to participating securities	18,204	16,119	41,502	35,813
Weighted average common shares outstanding	68,976	68,487	68,862	68,442
Basic net income per share	$ 0.26	$ 0.24	$ 0.60	$ 0.52
Diluted net income per share:
Net income applicable to common stockholders	18,307	16,236	41,842	36,106
Undistributed earnings allocated to participating securities	(103)	(117)	(340)	(293)
Net income applicable to common stockholders excluding amounts applicable to participating securities	$ 18,204	$ 16,119	$ 41,502	$ 35,813
Weighted average common shares outstanding	68,976	68,487	68,862	68,442
Dilutive shares from assumed conversion of convertible senior notes	1,949	0	1,806	0
Dilutive stock options and restricted stock	994	524	855	458
Diluted weighted average common shares outstanding	71,919	69,011	71,523	68,900
Diluted net income per share	$ 0.25	$ 0.23	$ 0.58	$ 0.52

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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