Cash and Cash Equivalents and Investments (Details 1) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Cash and Cash Equivalents
Fair Value
Amortized Cost	$ 26,775	$ 37,499
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	26,775	37,499
Certificates of Deposit
Fair Value
Amortized Cost	552	552
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	552	552
U.S. Treasury Securities
Fair Value
Amortized Cost	30,540	91,075
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	(1)
Estimated Fair Value	30,542	91,077
Total Short-term Investments
Fair Value
Amortized Cost	31,092	91,627
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	(1)
Estimated Fair Value	31,094	91,629
Total Cash and Cash Equivalents and Investments
Fair Value
Amortized Cost	57,867	129,126
Gross Unrealized Gains	2	3
Gross Unrealized Losses	0	(1)
Estimated Fair Value	$ 57,869	$ 129,128