Fair Value Disclosures - Fair Value of Other Financial Instruments Not Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	$ 241,469	$ 228,788	$ 111,524	$ 71,301
Convertible Notes	211,671	208,414
Fair value, measurements, nonrecurring [Member] | Fair Value [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	50,798	39,696
Convertible Notes	267,824	277,145
Fair value, measurements, nonrecurring [Member] | Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	50,798	39,696
Convertible Notes
Fair value, measurements, nonrecurring [Member] | 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	267,824	277,145
Fair value, measurements, nonrecurring [Member] | 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