Earnings Per Share Attributable to Common Stockholders (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share Attributable to Common Stockholders
Net loss	$ (13,640)	$ (4,611)	$ (38,595)	$ (17,436)
Weighted average common shares outstanding	76,880	59,799	68,315	58,096
Net loss per share - basic and diluted	$ (0.18)	$ (0.08)	$ (0.56)	$ (0.30)