Short-Term Investments - Available-for-Sale Securities Recorded at Fair Value with Unrealized Gains or Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	$ 1	$ 4,080
Gross unrealized gain (loss)		(2)
Fair value	1	4,078
Government Securities/Money Market [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	1	4,080
Gross unrealized gain (loss)		(2)
Fair value	$ 1	$ 4,078