Cash and Cash Equivalents and Short-Term Investments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Cash, cash equivalents and short-term investments
Operating Cash, Amortized Cost and Estimated Fair Value	$ 184	$ 53
Operating Cash, Gross Unrealized Gains
Operating Cash, Gross Unrealized Losses
Cash, cash equivalents amortized cost	21,703	34,308
Cash cash equivalents and short term investments unrealized gains		2
Cash cash equivalents and short term investments unrealized loses	1	1
Short term investments	15,188	25,161
Cash and cash equivalents fair value disclosure	21,702	34,309
Money Market Funds [Member]
Cash, cash equivalents and short-term investments
Cash, cash equivalents amortized cost	6,330	3,855
Cash cash equivalents and short term investments unrealized gains
Cash cash equivalents and short term investments unrealized loses
Cash and cash equivalents fair value disclosure	6,330	3,855
Government sponsored enterprise [Member]
Cash, cash equivalents and short-term investments
Cash, cash equivalents amortized cost	15,189	23,900
Cash cash equivalents and short term investments unrealized gains		2
Cash cash equivalents and short term investments unrealized loses	1	1
Cash and cash equivalents fair value disclosure	15,188	23,901
U S Treasury Securities [Member]
Cash, cash equivalents and short-term investments
Cash, cash equivalents amortized cost		6,500
Cash cash equivalents and short term investments unrealized gains
Cash cash equivalents and short term investments unrealized loses
Cash and cash equivalents fair value disclosure		$ 6,500