Short Term Investments (Tables)

6 Months Ended

Jun. 30, 2012

Short-Term Investments [Abstract]

Available-for-sale securities recorded at fair value with unrealized gains or losses

	Fair value		June 30,  2012 Amortized cost basis		Net unrealized loss			Fair value		December 31,  2011 Amortized cost basis		Net unrealized loss
Corporate notes, bonds and paper	$	13,532	$	13,533	$	(1	)	$	31,180	$	31,217	$	(33	)
Government securities		6,757		6,760		(3	)		7,317		7,321		(2	)
Total	$	20,289	$	20,293	$	(4	)	$	38,497	$	38,538	$	(35	)