Short-Term Investments - Available-for-Sale Securities Recorded at Fair Value with Unrealized Gains or Losses (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	$ 4,320	$ 2,881
Gross unrealized gain (loss)	1	(1)
Fair value	4,321	2,880
Corporate notes, bonds and paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis		1,000
Gross unrealized gain (loss)		(1)
Fair value		999
Government securities/money market [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	4,320	1,881
Gross unrealized gain (loss)	1
Fair value	$ 4,321	$ 1,881