Cash and Investments - Cash, Cash Equivalents, Short-Term Investments, and Restricted Cash (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Investment Holdings [Line Items]
Cash	$ 2,544	$ 2,521
Cash equivalents:
Total cash equivalents	8,558	10,989
Total cash and cash equivalents	11,102	13,510	10,771	9,903
Short-term investments:
Total short-term investments	13,029	7,295
Restricted cash-money market fund	250	250
Total cash, cash equivalents, investments and restricted cash	24,381	21,055
Corporate debt securities [Member]
Cash equivalents:
Total cash equivalents	1,252	2,000
Short-term investments:
Total short-term investments	11,831	4,794
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	1,198	1,500
Foreign government bonds [Member]
Short-term investments:
Total short-term investments	0	1,001
Money market funds [Member]
Cash equivalents:
Total cash equivalents	$ 7,306	$ 8,989