Convertible Senior Notes Due 2017 - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014 Trading_day
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