Common stock (Tables)

3 Months Ended

Mar. 31, 2014

Text Block [Abstract]

Schedule of Weighted Average Assumptions

The fair value of stock options granted is estimated using the Black-Scholes option pricing model with the following weighted average assumptions:

	THREE MONTHS ENDED MARCH 31, 2014			THREE MONTHS ENDED MARCH 31, 2013		DECEMBER 26, 2003 (INCEPTION) TO MARCH 31, 2014
Expected volatility		108	%		NA		88	%
Expected dividends		0	%		NA		0	%
Expected terms (years)		6.00			NA		6.24
Risk free rate		1.52	%		NA		2.96	%
Weighted average grant-date fair value of stock options	$	9.05			NA	$	4.23