Condensed Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5,319)us-gaap_NetIncomeLoss	$ (7,572)us-gaap_NetIncomeLoss
Change in unrealized gain on available-for-sale securities	50	9
Comprehensive loss	$ (5,269)us-gaap_ComprehensiveIncomeNetOfTax	$ (7,563)us-gaap_ComprehensiveIncomeNetOfTax

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration