Long-term Debt Obligations - 1.50% Convertible Senior Notes and Call Spread - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended				6 Months Ended			6 Months Ended		1 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 D	May 31, 2013	Dec. 31, 2012	Oct. 31, 2012	Jun. 30, 2013 Warrant [Member]	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Minimum [Member] Warrant [Member]	Jun. 30, 2013 Maximum [Member]	Jun. 30, 2013 Maximum [Member] Warrant [Member]	May 31, 2013 1.50% Convertible Senior Notes [Member]	Jun. 30, 2013 1.50% Convertible Senior Notes [Member]	Jun. 30, 2012 1.50% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Principal amount of convertible senior notes											$ 660,000,000
Debt instrument interest rate											1.50%	1.50%	1.50%
Debt instrument maturity date											Jun. 30, 2018
Proceeds from convertible senior notes, net of underwriting discounts and offering costs											648,000,000
Debt issuance costs											12,000,000	8,300,000
Debt payment due dates		Payable semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2013
Debt, interest expenses	1,300,000
Convertible principal amount		1,000
Convertible instrument, shares issued		8.0306
Debt instrument convertible, conversion price per share	$ 124.52	$ 124.52
Debt instrument convertible consecutive trading days							20 days		30 days
Debt instrument convertible trading days		5
Debt instrument convertible, percentage of conversion price	130.00%	130.00%
Average percentage of closing sale price of common stock		98.00%
Percentage of repurchase price is equal to principal amount of convertible notes		100.00%
Debt conversion, converted instrument, amount		82,800,000
Debt instrument, effective interest rate	4.29%	4.29%
Amortization of debt discount		1,582,000
Long-term debt, less current portion	578,740,000	578,740,000		401,495,000
Payment for purchase of common stock	5,300,000	5,300,000
Common stock purchase price	$ 124.52	$ 124.52
Hedge transaction		177,500,000
Common stock share issued	121,429,665	121,429,665	3,902,862	114,214,274	7,964,601	5,300,000
Common stock par value	$ 0.001	$ 0.001		$ 0.001		$ 184.48
Proceeds from issuance of warrants		$ 120,318,000				$ 120,300,000
Conversion price per share								$ 124.52		$ 184.48