Fair Value Disclosures - Fair Value of Other Financial Instruments Not Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	$ 290,036	$ 228,788	$ 100,987	$ 71,301
Convertible Notes	215,022	208,414
Fair value, measurements, nonrecurring [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	97,671	39,696
Convertible Notes	298,499	277,145
Fair value, measurements, nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Bank deposits (included in "Cash and cash equivalents")	97,671	39,696
Fair value, measurements, nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Notes	$ 298,499	$ 277,145