Stockholders' Equity and Redeemable Convertible Preferred Stock (Details 6) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Total compensation expense	$ 89	$ 1,581		$ 223	$ 11,954
Employee restricted stock awards [Member]
Total compensation expense	0		$ 19	11	33
Employee stock option awards [Member]
Total compensation expense	64		1,547	154	11,698
Non-employee restricted stock awards [Member]
Total compensation expense	25		15	58	175
Non-employee option awards [Member]
Total compensation expense	$ 0		$ 0	$ 0	$ 48