Cash and Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010
Cash, cash equivalents, short-term investments, long-term investments and restricted cash
Cash	$ 2,590				$ 1,428
Cash and cash equivalents:
Total cash equivalents	7,313				7,077
Total cash and cash equivalents	9,903	6,897	10,515	7,233	8,505	9,053	8,510	8,304	10,814
Short-term investments:
Total short-term investments	9,826				9,619
Total cash, cash equivalents, investments and restricted cash	20,604				18,999
Corporate debt [Member]
Cash and cash equivalents:
Total cash equivalents					501
Money market funds [Member]
Cash and cash equivalents:
Total cash equivalents	7,313				6,576
Short-term investments:
Restricted cash-money market fund	875				875
U.S. agency securities [Member]
Short-term investments:
Total short-term investments					1,751
Municipal securities [Member]
Short-term investments:
Total short-term investments	356				355
Corporate commercial paper [Member]
Short-term investments:
Total short-term investments	4,374				1,250
Foreign government bonds [Member]
Short-term investments:
Total short-term investments	999				500
Corporate debt securities [Member]
Short-term investments:
Total short-term investments	$ 4,097				$ 5,763