Stockholders' Equity and Warrants Valuation Assumptions of Convertible Preferred Stock Warrants Under Monte Carlo Simulation Model (Details) (Convertible Preferred Stock Warrant Liability [Member], Convertible preferred stock)	12 Months Ended
	Dec. 31, 2012
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Dividend yield	0.00%
Minimum
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Expected term (in years)	4 years 6 months
Expected volatility	60.50%
Annual risk-free rate of return	1.50%
Maximum
Fair Value Assumptions and Methodology for Assets and Liabilities [Abstract]
Expected term (in years)	6 years
Expected volatility	73.00%
Annual risk-free rate of return	2.70%