Cash and Investments - Cash, Cash Equivalents, Short-Term Investments, and Restricted Cash (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Schedule of Investments [Abstract]
Cash	$ 3,297	$ 2,590
Total cash and cash equivalents	13,236	9,903	6,897	8,505
Short-term investments:
Total short-term investments	8,053	9,826
Restricted cash-money market fund	250	875
Total cash, cash equivalents, short-term investments and restricted cash	21,539	20,604
Municipal securities [Member]
Short-term investments:
Total short-term investments		356
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	1,250	4,374
Foreign government bonds [Member]
Short-term investments:
Total short-term investments	1,001	999
Corporate debt securities [Member]
Short-term investments:
Total short-term investments	5,802	4,097
Cash equivalents-money market fund [Member]
Schedule of Investments [Abstract]
Cash equivalents-money market fund	$ 9,939	$ 7,313