Bridge Financing (Details) (USD $)	1 Months Ended	3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended	81 Months Ended
	Jan. 31, 2013	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012 Series B Redeemable Convertible Preferred Stock Warrants	Jun. 30, 2012 Series B Redeemable Convertible Preferred Stock Warrants	Oct. 31, 2012 Series B Redeemable Convertible Preferred Stock Warrants	Dec. 31, 2006 Series B Redeemable Convertible Preferred Stock Warrants
Bridge Financing
Shares issuable upon exercise of warrants (in shares)									243,000
Exercise price of warrants (in dollars per share)									$ 7.6055
Dividend yield (as a percent)							0.00%
Risk-free interest rate (as a percent)							0.17%
Volatility rate (as a percent)							58.00%
Increase in fair value								$ 1,205,000
Warrant and other interest income (expense), net		$ (577,000)	$ (476,000)			$ (467,000)	$ (381,000)
Warrants outstanding (in shares)				0	178
Shares of common stock issued as a result of exercise of warrants	153,000