Fair Value (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Fair value (Textual) [Abstract]
Net asset value per share used to value money market and U.S. Treasury debt securities	$ 1.00
Transfers of financial assets between Level 1 and Level 2	$ 0	$ 0

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

Name:	us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant