Cash and Investments - Cash, Cash Equivalents, Short-Term Investments, and Restricted Cash (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Investment Holdings [Line Items]
Cash	$ 2,508	$ 2,521
Cash equivalents:
Total cash equivalents	14,337	10,989
Total cash and cash equivalents	16,845	13,510	10,177	9,903
Short-term investments:
Total short-term investments	6,131	7,295
Restricted cash-money market fund	250	250
Total cash, cash equivalents, short-term investments and restricted cash	23,226	21,055
Corporate debt securities [Member]
Cash equivalents:
Total cash equivalents	652	2,000
Short-term investments:
Total short-term investments	4,881	4,794
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	1,250	1,500
Foreign government bonds [Member]
Short-term investments:
Total short-term investments		1,001
Money market funds [Member]
Cash equivalents:
Total cash equivalents	12,435	8,989
Corporate commercial paper [Member]
Cash equivalents:
Total cash equivalents	$ 1,250