Fair Value - Summary of Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Assets measured at fair value
Cash and cash equivalents	$ 52,566	$ 10,014
Restricted cash	250	375	375
Short term investments		6,191
Total	52,816	16,580
Fair Value, Inputs, Level 1 [Member]
Assets measured at fair value
Cash and cash equivalents	52,566	10,014
Restricted cash	250	375
Total	52,816	10,389
Fair Value, Inputs, Level 2 [Member]
Assets measured at fair value
Short term investments		6,191
Total		$ 6,191