Short-Term Investments - Available-for-Sale Securities Recorded at Fair Value with Unrealized Gains or Losses (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	$ 3,800	$ 2,881
Gross unrealized gain (loss)		(1)
Fair value	3,800	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	3,800	1,881
Fair value	$ 3,800	$ 1,881