Calculation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Basic net income per share:
Net income applicable to common stockholders	$ 10,474	$ 7,296
Undistributed earnings allocated to participating securities	0	(61)
Net income applicable to common stockholders excluding amounts applicable to participating securities	10,474	7,235
Weighted average common shares outstanding	68,731	68,669
Basic net income per share	$ 0.15us-gaap_EarningsPerShareBasic	$ 0.11us-gaap_EarningsPerShareBasic
Diluted net income per share:
Net income applicable to common stockholders	10,474	7,296
Undistributed earnings allocated to participating securities	0	(61)
Net income applicable to common stockholders excluding amounts applicable to participating securities	$ 10,474	$ 7,235
Weighted average common shares outstanding	68,731	68,669
Dilutive shares from assumed conversion of convertible senior notes	1,729	1,591
Dilutive stock options and restricted stock	1,095	828
Diluted weighted average common shares outstanding	71,555	71,088
Diluted net income per share	$ 0.15us-gaap_EarningsPerShareDiluted	$ 0.1us-gaap_EarningsPerShareDiluted

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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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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