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	3 Months Ended
	Mar. 31, 2014	Mar. 31, 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	2,051	(3)
Balance at end of period	485
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
Exercise of common stock warrants	(2,505)
Remeasurement of common stock warrants	2,051	(3)
Balance at end of period	485	7
Warrant [Member]
Summary of Significant Accounting Policies (Details) - Reconciliation of the warrant liability measured at fair value using Level 3 inputs [Line Items]
Remeasurement of common stock warrants	$ 2,500