Convertible and Long-term Debt Obligations - 0.25% and 1.25% Convertible Senior Notes and Bond Hedge and Warrant Transactions - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	9 Months Ended			9 Months Ended			1 Months Ended	9 Months Ended		9 Months Ended	3 Months Ended	9 Months Ended		1 Months Ended					1 Months Ended
	Apr. 30, 2014	Mar. 31, 2014	Sep. 30, 2014 D	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 0.25% Convertible senior notes due 2019 [Member]	Apr. 30, 2014 0.25% Convertible senior notes due 2019 [Member]	Mar. 31, 2014 0.25% Convertible senior notes due 2019 [Member]	Mar. 31, 2014 1.25% Convertible senior notes due 2021 [Member]	Sep. 30, 2014 1.25% Convertible senior notes due 2021 [Member]	Apr. 30, 2014 1.25% Convertible senior notes due 2021 [Member]	Sep. 30, 2014 0.25% and 1.25% Convertible Senior Notes and Bond Hedge and Warrant Transactions [Member] D	Dec. 31, 2014 0.25% and 1.25% Convertible Senior Notes and Bond Hedge and Warrant Transactions [Member] Scenario, Forecast [Member] D	Sep. 30, 2014 Minimum [Member] 0.25% and 1.25% Convertible Senior Notes and Bond Hedge and Warrant Transactions [Member]	Sep. 30, 2014 Maximum [Member] 0.25% and 1.25% Convertible Senior Notes and Bond Hedge and Warrant Transactions [Member]	Apr. 30, 2014 Warrants [Member]	Mar. 31, 2014 Warrants [Member]	Sep. 30, 2014 Warrants [Member]	Apr. 30, 2014 Warrants [Member] 0.25% Convertible senior notes due 2019 [Member]	Mar. 31, 2014 Warrants [Member] 0.25% Convertible senior notes due 2019 [Member]	Mar. 31, 2014 Warrants [Member] 1.25% Convertible senior notes due 2021 [Member]	Apr. 30, 2014 Warrants [Member] 1.25% Convertible senior notes due 2021 [Member]	Sep. 30, 2014 Warrants [Member] Minimum [Member]	Apr. 30, 2014 Warrants [Member] Minimum [Member] 0.25% Convertible senior notes due 2019 [Member]	Apr. 30, 2014 Warrants [Member] Minimum [Member] 1.25% Convertible senior notes due 2021 [Member]	Sep. 30, 2014 Warrants [Member] Maximum [Member]	Apr. 30, 2014 Warrants [Member] Maximum [Member] 0.25% Convertible senior notes due 2019 [Member]	Apr. 30, 2014 Warrants [Member] Maximum [Member] 1.25% Convertible senior notes due 2021 [Member]
Debt Instrument [Line Items]
Principal amount of convertible senior notes			$ 659,800,000	$ 659,800,000		$ 660,000,000		$ 120,000,000	$ 800,000,000	$ 1,200,000,000		$ 180,000,000
Debt instrument interest rate									0.25%	1.25%
Proceeds from convertible senior notes, total net of underwriting discounts and offering costs	267,600,000						905,800,000			1,780,000,000	1,360,000,000
Debt issuance costs							14,200,000				21,400,000
Debt instrument maturity year							2019				2021
Debt payment due dates				The interest rates are fixed at 0.25% and 1.25% per annum and are payable semi-annually in arrears on March 1 and September 1 of each year, commencing on September 1, 2014.
Debt, interest expense			1,000,000	2,200,000
Coupon interest expense			4,900,000	11,200,000
Convertible principal amount													1,000
Convertible instrument, shares issued													2.7788
Debt instrument convertible, conversion price per share													$ 359.87
Debt instrument convertible consecutive trading days			30 days											30 days	20 days	30 days
Debt instrument convertible trading days			20										5	20
Debt instrument convertible, percentage of conversion price													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%
Common stock price to conversion price, percentage			130.00%											130.00%
Debt conversion, converted instrument, amount							188,100,000				369,400,000
Debt instrument, effective interest rate			4.29%	4.29%			4.89%				5.96%
Amortization of debt discount			19,600,000	55,634,000	5,344,000
Long-term debt, less current portion			597,600,000	597,600,000			751,200,000				1,040,000,000
Payment for purchase of common stock		5,600,000
Common stock purchase price		$ 359.87
Hedge transactions		524,700,000								524,700,000							78,700,000
Common stock share issued			125,366,171	125,366,171		123,090,990													5,300,000	300,000	2,200,000	3,300,000	500,000
Common stock par value			$ 0.001	$ 0.001		$ 0.001													$ 184.48	$ 512.66	$ 512.66	$ 560.64	$ 560.64
Proceeds from issuance of warrants				$ 389,160,000	$ 120,318,000												$ 50,800,000	$ 338,400,000				$ 338,400,000
Conversion price per share																								$ 124.52	$ 359.87	$ 359.87	$ 184.48	$ 512.66	$ 560.64