Summary of Significant Accounting Policies (Details) - Reconciliation of the warrant liability measured at fair value using Level 3 inputs (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Summary of Significant Accounting Policies (Details) - Reconciliation of the warrant liability measured at fair value using Level 3 inputs [Line Items]
Balance at beginning of period	$ 939
Exercise of common stock warrants	2,500
Remeasurement of common stock warrants	1,682	(6)
Balance at end of period	1,647
Warrant [Member] | Fair Value, Inputs, Level 3 [Member]
Summary of Significant Accounting Policies (Details) - Reconciliation of the warrant liability measured at fair value using Level 3 inputs [Line Items]
Balance at beginning of period	939	10
Issuance of common stock warrants	1,531
Exercise of common stock warrants	(2,505)
Remeasurement of common stock warrants	1,682	(6)
Balance at end of period	$ 1,647	$ 4