Short-Term Investments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 20,289	$ 38,497
Amortized cost basis	(20,293)	(38,538)
Net unrealized loss	(4)	(35)
Corporate notes, bonds and paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	13,532	31,180
Amortized cost basis	(13,533)	(31,217)
Net unrealized loss	(1)	(33)
Government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value	6,757	7,317
Amortized cost basis	(6,760)	(7,321)
Net unrealized loss	$ (3)	$ (2)