Cash and Investments - Cash, Cash Equivalents, Short-Term Investments, and Restricted Cash (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Schedule of Investments [Abstract]
Cash	$ 2,521				$ 2,590
Total cash and cash equivalents	13,510	13,236	10,771	10,177	9,903	6,897	10,515	7,233	8,505
Short-term investments:
Total short-term investments	7,295				9,826
Restricted cash-money market fund	250				875
Total cash, cash equivalents, short-term investments and restricted cash	21,055				20,604
Municipal securities [Member]
Short-term investments:
Total short-term investments					356
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	1,500				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	4,794				4,097
Cash equivalents-money market fund [Member]
Schedule of Investments [Abstract]
Cash equivalents - money market funds	$ 10,989				$ 7,313