Cash and Investments (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Cash, cash equivalents, short-term investments, long-term investments and restricted cash
Cash	$ 1,994,000	$ 2,590,000
Cash equivalents:
Total cash equivalents	8,777,000	7,313,000
Total cash and cash equivalents	10,771,000	9,903,000	10,515,000	8,505,000
Short-term investments:
Total short-term investments	9,331,000	9,826,000
Restricted cash-money market fund	875,000	875,000
Total cash, cash equivalents, investments and restricted cash	20,977,000	20,604,000
Money market funds [Member]
Cash equivalents:
Total cash equivalents	8,777,000	7,313,000
Municipal Securities [Member]
Short-term investments:
Total short-term investments		356,000
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	1,250,000	4,374,000
Foreign government bonds [Member]
Short-term investments:
Total short-term investments	1,001,000	999,000
Corporate debt securities [Member]
Short-term investments:
Total short-term investments	$ 7,080,000	$ 4,097,000