Short-Term Investments - Available-for-Sale Securities Recorded at Fair Value with Unrealized Gains or Losses (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	$ 7,200	$ 13,336
Gross unrealized gain (loss)	(4)	(8)
Fair value	7,196	13,328
Corporate notes, bonds and paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis		9,091
Gross unrealized gain (loss)		(7)
Fair value		9,084
Government securities/money market [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost basis	7,200	4,245
Gross unrealized gain (loss)	(4)	(1)
Fair value	$ 7,196	$ 4,244