Short-Term Investments - Available-for-Sale Securities Recorded at Fair Value with Unrealized Gains or Losses (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	$ 1,680	$ 4,080
Gross unrealized gain (loss)	(1)	(2)
Fair value	1,679	4,078
Government securities/money market [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	1,680	4,080
Gross unrealized gain (loss)	(1)	(2)
Fair value	$ 1,679	$ 4,078