Convertible Senior Notes Due 2017 - Additional Information (Detail) (USD $)	9 Months Ended
Sep. 30, 2014 D
Debt Disclosure [Abstract]
Convertible Notes, maturity date	Apr. 01, 2017
Convertible Notes, payment terms	The Company pays interest semi-annually in arrears on April 1 and October 1 of each year.
Convertible Notes, aggregate principal amount	$ 258,800,000
Maximum percentage of conversion price upon redemption of Convertible Notes	130.00%
Percentage of redemption price to principal amount of note	100.00%
Convertible Notes, conversion term description	(1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2012, if the closing sale price of the Company's common stock, for at least 20 trading days (whether or not consecutive) in the period of 30 consecutive trading days ending on the last trading day of the calendar quarter immediately preceding the calendar quarter in which the conversion occurs, is more than 130% of the conversion price of the Convertible Notes in effect on each applicable trading day; (2) during the five consecutive trading-day period following any five consecutive trading-day period in which the trading price for the Convertible Notes for each such trading day is less than 98% of the closing sale price of the Company's common stock on such date multiplied by the then-current conversion rate; (3) upon the occurrence of specified corporate events; or (4) if the Company calls any Convertible Notes for redemption, at any time until the close of business on the second business day preceding the redemption date. On or after January 1, 2017 until the close of business on the second business day immediately preceding the stated maturity date, holders may surrender their Convertible Notes for conversion at any time, regardless of the foregoing circumstances.
Number of trading days	20
Consecutive trading days	30 days
Conversion rate of common stock, shares per principal amount	19.5172
Debt instrument convertible increment of principal amount of conversion	$ 1,000
Conversion price, per share of common stock	$ 51.24

Increment of of principal amount of convertible debt subject to conversion.

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Threshold percentage that common stock price to conversion price of convertible debt instruments must exceed within a specified consecutive trading period to trigger conversion feature.

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Percentage of the principal amount of the Convertible Notes to be redeemed.

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The price per share of the conversion feature embedded in the debt instrument.

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Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Description of the conversion terms of a debt instrument which may include the conversion ratio (including all potential conversion ratios if contingently adjustable), type of debt or equity security into which the debt is convertible, the dollars of debt or the number of shares into which the instrument is convertible (or potentially convertible into), the conversion period, any contingencies associated with the conversion terms, and the existence and amount of a beneficial conversion feature.

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Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instruments must exceed threshold percentage for a specified number of trading days to trigger conversion feature, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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