Convertible Preferred Stock Warrant Liability (Tables)

12 Months Ended

Dec. 31, 2013

Estimated Fair Value for Each of the Convertible Preferred Stock Warrants

Upon closing of the IPO, all convertible preferred stock warrants converted into warrants to purchase shares of common stock at a conversion rate of 1-for-1 and the estimated liability was reclassified to additional paid-in capital. The following table sets forth the estimated fair value for each of the convertible preferred stock warrants as of May 22, 2013, the date of the final remeasurement before reclassifying the liability to APIC, and December 31, 2012 (in thousands, except share and per share data):

				Shares as of		Estimated Fair Value
		Exercise
Preferred		Price		May 22,	December 31,	May 22,		December 31,
Stock	Expiration Date	Per Share		2013	2012	2013		2012
Series A	Later of: (i) January 20, 2015 or (ii) 3 years after the closing of an initial public offering of our common stock	$	10.00	4,740	4,740	$	35	$	36
Series B	Later of: (i) September 28, 2016 or (ii) 5 years after the closing of an initial public offering of our common stock	$	13.10	76,335	76,335		624		647
Total				81,075	81,075	$	659	$	683

Fair Values of Employee Stock Options

The estimated fair value of the above warrants was determined using the Black-Scholes option-pricing model using the following assumptions:

	May 22,		December 31,
	2013		2012
Risk-free interest rate	0.1 - 0.9%		0.3 - 0.6%
Estimated term equal to the remaining contractual term	1.7 - 3.8 years		2.1 - 4.2 years
Volatility		79%		82%
Dividend yield	–		–