Stock-Based Compensation (Details 3) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended	12 Months Ended							1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 28, 2011 Initial public offering	Dec. 28, 2012 Public Offering of Common Stock	Dec. 31, 2012 Stock option	Dec. 31, 2011 Stock option	Dec. 31, 2010 Stock option	Dec. 31, 2011 Stock option Minimum	Dec. 31, 2010 Stock option Minimum	Dec. 31, 2011 Stock option Maximum	Dec. 31, 2010 Stock option Maximum	Jul. 31, 2007 Stock option Employees	Dec. 31, 2012 Stock option Employees	Dec. 31, 2011 Stock option Employees	Dec. 31, 2010 Stock option Employees	Jul. 31, 2007 Stock option Non-employees	Dec. 31, 2012 Stock option Non-employees	Dec. 31, 2011 Stock option Non-employees	Dec. 31, 2010 Stock option Non-employees	Dec. 31, 2012 Restricted stock awards	Dec. 31, 2011 Restricted stock awards
Stock-Based Compensation
Cumulative grant date fair value														$ 347,000	$ 244,000	$ 118,000
Intrinsic value of options exercised														0	58,000	0
Proceeds received for options exercised	1,000	88,000												500	87,500	0
Compensation expense related to unvested employee stock options not yet recognized						577,000	944,000	608,000
Weighted-average period of recognition						2 years 3 months 11 days	2 years 8 months 19 days	1 year 10 months 17 days
Vesting period													4 years				3 years				4 years
Stock-based compensation	$ 588,000	$ 492,000	$ 625,000															$ 20,000	$ 30,000	$ 388,000	$ 255,000	$ 159,000
Assumptions used
Risk free interest rate, minimum (as a percent)							1.24%	2.45%
Risk free interest rate, maximum (as a percent)							2.63%	2.82%
Risk free interest rate (as a percent)						0.92%
Dividend yield (as a percent)						0.00%	0.00%	0.00%
Expected volatility (as a percent)						57.00%	53.00%	50.00%
Expected term						6 years 3 months			5 years 9 months	5 years 9 months	6 years 3 months	6 years 3 months
Weighted average grant date fair value (in dollars per share)						$ 0.54	$ 1.76	$ 3.56
Number of Shares
Awards outstanding at the beginning of the period (in shares)																					135,000
Granted (in shares)																						135,000
Vested (in shares)																					(67,500)
Awards outstanding at the end of the period (in shares)																					67,500	135,000
Weighted Average Fair Value
Awards outstanding at the beginning of the period (in dollars per share)																					$ 5.89
Granted (in dollars per share)																						$ 5.89
Vested (in dollars per share)																					$ 3.79
Awards outstanding at the end of the period (in dollars per share)																					$ 8.00	$ 5.89
Common Stock Purchase Options issued to underwriters
Issuance of option to purchase common stock (in shares)				103,125	500,000
Exercise price of options issued to underwriters (in dollars per share)				$ 10.00	$ 0.8125
Exercise price of options as a percentage of purchase price of shares sold in initial public offering				125.00%	125.00%
Term of options issued to underwriters				5 years	5 years
Term after effective date of IPO after which stock options to underwriters become exercisable				1 year	1 year