Fair Value Measurements (Details 1) (Convertible Preferred Stock, USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Convertible Preferred Stock
Beginning and ending balances for the Company's fair value measurements using Level 3 inputs
Asset, Beginning Balance	$ 25,720	$ 17,220
Unrealized gains (losses) included in other comprehensive income	(5,190)	490
Asset, Ending Balance	$ 20,530	$ 17,710

Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1a)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

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