Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net loss	$ (11,065)	$ (4,295)	$ (11,901)	$ (8,748)
Other comprehensive income / (loss):
Amounts reclassified for net realized losses on available-for-sale securities included in net loss	0	6	491	373
Net unrealized losses on available-for-sale securities occurring during the period	0	(54)	(22)	(349)
Other comprehensive (loss) / income	0	(48)	469	24
Total comprehensive loss	$ (11,065)	$ (4,343)	$ (11,432)	$ (8,724)