Cash and Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Cash, cash equivalents, short-term investments, long-term investments and restricted cash
Cash	$ 4,239	$ 2,590
Cash equivalents:
Total cash equivalents	5,938	7,313
Total cash and cash equivalents	10,177	9,903	7,233	8,505
Short-term investments:
Total short-term investments	9,245	9,826
Total cash, cash equivalents, investments and restricted cash	20,297	20,604
Money market funds [Member]
Cash equivalents:
Total cash equivalents	5,938	7,313
Short-term investments:
Restricted cash-money market fund	875	875
Municipal Securities [Member]
Short-term investments:
Total short-term investments		356
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	1,475	4,374
Foreign government bonds [Member]
Short-term investments:
Total short-term investments	1,000	999
Corporate debt securities [Member]
Short-term investments:
Total short-term investments	$ 6,770	$ 4,097