Basic and Diluted Net Loss Attributable to Common Stockholders per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		146 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Numerator:
Net loss attributable to common stockholders	$ (15,943)	$ (17,458)	$ (414,691)
Denominator
Weighted average common shares outstanding - basic and diluted	64,353,952	49,621,188
Common stock options
Antidilutive securities
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	11,300,000	10,500,000