Convertible Notes with and without Embedded Derivative and Fair Value of Embedded Derivative (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair value of Convertible Notes:
With the embedded derivatives	$ 20,310	$ 15,925
Without the embedded derivatives	18,104	12,455
Estimated fair value of the embedded derivatives	$ 2,206	$ 3,470