Convertible Notes and Long-term Debt Obligations - 1.50% Convertible Senior Notes and Bond Hedge and Warrant Transactions - Additional Information (Detail)	1 Months Ended			3 Months Ended	12 Months Ended
	Apr. 30, 2014 USD ($)	Mar. 31, 2014 USD ($) $ / shares shares	May. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) d $ / shares shares	Dec. 31, 2015 USD ($) d $ / shares shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of warrants						$ 389,160,000	$ 120,318,000
Senior Notes [Member]
Debt Instrument [Line Items]
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%
Payment for purchase of common stock | shares		5,600,000
Common stock purchase price | $ / shares		$ 359.87
Hedge transactions		$ 524,700,000
Senior Notes [Member] | Warrants [Member]
Debt Instrument [Line Items]
Hedge transactions	$ 78,700,000
Proceeds from issuance of warrants	$ 50,800,000
Senior Notes [Member] | 1.50% Convertible senior notes due 2018 [Member]
Debt Instrument [Line Items]
Principal amount of convertible senior notes			$ 660,000,000	$ 659,761,000	$ 659,761,000	659,762,000
Debt instrument interest rate			1.50%
Debt instrument maturity year					2018
Proceeds from convertible senior notes, net of underwriting discounts and offering costs			$ 648,000,000
Debt issuance costs			$ 12,000,000
Debt instrument interest payment description					payable semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2013
Convertible principal amount					$ 1,000
Convertible instrument, shares issued | shares					8.0306
Convertible notes, conversion price | $ / shares				$ 124.52	$ 124.52
Debt instrument convertible consecutive trading days				30 days
Debt instrument convertible trading days | d				20	5
Debt instrument convertible, percentage of conversion price				130.00%	130.00%
Average percentage of closing sale price of common stock					98.00%
Debt instrument, effective interest rate				4.29%	4.29%
Payment for purchase of common stock | shares				5,300,000	5,300,000
Common stock purchase price | $ / shares				$ 124.52	$ 124.52
Hedge transactions					$ 177,500,000
Shares issued under warrants | shares				5,300,000	5,300,000
Exercise price of warrant | $ / shares				$ 184.48	$ 184.48
Common stock price to conversion price, percentage				130.00%
Notes carrying value				$ 617,700,000	$ 617,700,000
Unamortized debt discount				$ 42,045,000	42,045,000	$ 58,196,000
Senior Notes [Member] | 1.50% Convertible senior notes due 2018 [Member] | Warrants [Member]
Debt Instrument [Line Items]
Proceeds from issuance of warrants					$ 120,300,000
Senior Notes [Member] | 1.50% Convertible senior notes due 2018 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument convertible consecutive trading days					20 days
Senior Notes [Member] | 1.50% Convertible senior notes due 2018 [Member] | Minimum [Member] | Warrants [Member]
Debt Instrument [Line Items]
Convertible notes, conversion price | $ / shares				$ 124.52	$ 124.52
Senior Notes [Member] | 1.50% Convertible senior notes due 2018 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument convertible consecutive trading days					30 days
Senior Notes [Member] | 1.50% Convertible senior notes due 2018 [Member] | Maximum [Member] | Warrants [Member]
Debt Instrument [Line Items]
Convertible notes, conversion price | $ / shares				$ 184.48	$ 184.48