Net Loss per Common Share (Antidilutive Securities) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Antidilutive Securities Excluded from Computation of Earnings Per Share
Potentially dilutive securities excluded from computation of diluted net loss per share	3,752,413	3,515,051	11,371,090
IPO price for conversion computations	$ 7.00
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Potentially dilutive securities excluded from computation of diluted net loss per share	0	0	8,438,417	[1]
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share
Potentially dilutive securities excluded from computation of diluted net loss per share	0	0	0
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Potentially dilutive securities excluded from computation of diluted net loss per share	3,752,413	3,515,051	2,932,673

[1] Amounts for the Series BB, C, D and E preferred stock conversions are computed based on the initial public offering price of 7.00 per share.