Convertible Senior Notes Due 2017 - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	Sep. 21, 2012	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt instrument, offering date		Mar. 19, 2012
Convertible Notes, maturity date		Apr. 01, 2017
Convertible Notes, payment terms		The Convertible Notes bear interest at a rate of 2.625% per annum, payable semi-annually in arrears on April 1 and October 1 of each year, beginning on October 1, 2012.
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 was 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. At December 31, 2012, the Convertible Notes were not convertible.
Debt instrument convertible conversion ratio presplit	9.7586
Debt instrument convertible increment of principal amount of conversion	1,000	1,000
Debt instrument convertible conversion price1 presplit	$ 102.47
Forward stock split of common stock		2
Conversion rate of common stock, shares per principal amount	19.5172
Conversion price, per share of common stock	$ 51.24
Amortization of debt discount		12,400,000	8,900,000
Convertible Notes, net of unamortized discount		208,414,000	196,007,000
Recognized debt discount		50,336,000	62,743,000
Issuance costs		8,400,000
Convertible Notes, issuance costs allocated to equity component		2,300,000
Convertible Notes, issuance costs allocated to debt component		6,100,000
Interest expense on Convertible Notes		20,249,000	14,985,000
Non-cash interest expense		13,456,000	9,663,000
2.625% convertible senior notes due 2017 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		2.625%	2.625%
Debt instrument, effective percentage rate		10.71%	10.71%
Interest expense on Convertible Notes		20,200,000	15,000,000
Cash interest expense		6,800,000	5,300,000
Non-cash interest expense		13,400,000	9,700,000
Equity component [Member]
Debt Instrument [Line Items]
Convertible Notes, equity component		71,700,000
Debt component [Member]
Debt Instrument [Line Items]
Debt instrument convertible debt equity component		$ 187,100,000
Common stock [Member]
Debt Instrument [Line Items]
Forward stock split of common stock	2	2