Fair Value Disclosures - Fair Value of Other Financial Instruments Not Measured on Recurring Basis (Detail) (Fair value, measurements, nonrecurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Convertible Notes	$ 327,900
Fair value [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	50,831	22,608
Convertible Notes	237,070	234,813
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	50,831	22,608
Convertible Notes
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")
Convertible Notes	237,070	234,813
Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")
Convertible Notes