Debt - Additional Information (Detail) (USD $)	3 Months Ended	1 Months Ended	3 Months Ended	1 Months Ended
	Mar. 31, 2013	Apr. 30, 2014 Subsequent Event	Jun. 30, 2014 Scenario, Forecast	Mar. 31, 2014 Senior Subordinated Convertible Notes
Debt Instrument [Line Items]
Debt instrument aggregate principal amount repurchased consideration		$ 523,000,000
Loss on the extinguishment of debt	17,100,000		54,000,000
Private offering senior subordinated convertible notes, aggregate principal amount				690,000,000
Interest rate of debt instrument				1.125%
Debt instrument maturity year				2034
Net proceeds after deducting fees and expenses				674,000,000
Initial conversion rate for common stock				13.36
Convertible note, initial conversion price per share				$ 74.86
Principal amount of convertible notes in to shares common stock				1,000
Percentage by which closing sale price of common stock is more than the current conversion price				130.00%
Number of trading days				20 days
Number of Consecutive trading days				30 days
Number Of Trading Days				60 days
Number of consecutive trading days immediately preceding, but excluding, declaration date				10 days
Percentage that distribution has per share value exceeding closing sale price of common stock				10.00%
Percentage of closing sale price of common stock in excess of convertible notes trading price				98.00%
Trading-day period				10 days
Convertible Debt Initial Liability Component				470,800,000
Convertible Debt Equity Component				$ 219,200,000
Effective interest rate				5.50%