Cash and Investments - Cash, Cash Equivalents, Short-Term Investments, and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment Holdings [Line Items]
Cash	$ 7,270	$ 2,763
Cash equivalents:
Total cash and cash equivalents	16,443	13,127	$ 13,510
Short-term investments:
Total short-term investments	13,280	13,263
Restricted cash equivalents—money market fund	250	250
Total cash, cash equivalents, short-term investments and restricted cash equivalents	29,973	26,640
Corporate commercial paper [Member]
Cash equivalents:
Total cash equivalents	5,404	9,362
Short-term investments:
Total short-term investments	6,245	550
Corporate debt securities [Member]
Cash equivalents:
Total cash equivalents	2,269	1,002
Short-term investments:
Total short-term investments	6,028	$ 12,713
Treasury bonds [Member]
Short-term investments:
Total short-term investments	1,007
Money market funds [Member]
Cash equivalents:
Total cash equivalents	$ 1,500