Other Debt - Convertible Senior Note Offering (Detail) (USD $)	12 Months Ended					0 Months Ended	3 Months Ended		0 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Jul. 29, 2013	Sep. 30, 2013	Dec. 31, 2013	Dec. 10, 2013
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt	$ 967,786,000	[1]	$ 0	[1]	$ 0
Long-term Debt	1,108,316,000							1,108,316,000
Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt						300,000,000
Convertible Senior Notes [Member] | Original 2018 Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt							10,000,000
Long-term Debt, Fair Value	299,600,000							299,600,000
Debt Instrument, Unamortized Discount	10,400,000							10,400,000
Convertible Senior Notes [Member] | Original 2018 Notes [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Debt Instrument [Line Items]
Long-term Debt, Fair Value	300,500,000							300,500,000
Debt Instrument, Convertible, Conversion Price, Per Conversion								59.805
Shares Converted Per Amount								1,000
Convertible Senior Notes [Member] | Original 2018 Notes [Member] | Underwriter's Option to Purchase Addtional Notes, Proceeds [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt							10,000,000
Convertible Senior Notes [Member] | Reopened 2018 Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt									287,500,000
Long-term Debt, Fair Value	282,100,000							282,100,000
Debt Instrument, Unamortized Discount	5,400,000							5,400,000
Convertible Senior Notes [Member] | Reopened 2018 Notes [Member] | Underwriter's Option to Purchase Addtional Notes, Proceeds [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt							287,500,000
Long-term Debt, Fair Value	282,100,000							282,100,000
Convertible Senior Notes [Member] | 2020 Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of convertible debt									402,500,000
Long-term Debt, Fair Value	389,700,000							389,700,000
Debt Instrument, Unamortized Discount	27,500,000							27,500,000	12,800,000
Debt Instrument, Convertible, Conversion Price, Per Conversion								66.0262
Shares Converted Per Amount								1,000
Long-term Debt	$ 389,700,000							$ 389,700,000

[1] For discussion on the restatement adjustments, see Note 2 - Restatement of Previously Issued Financial Statements.