Income Taxes -Schedule of Significant Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Accrued expenses	$ 912	$ 559
Intangible assets	527	603
Restricted stock	301	436
Fixed assets		2
Non-qualified stock options	1,558	440
Research and development credits	1,829	1,589
Net operating loss carryforward	51,356	30,559
Other	64	39
Total deferred tax assets	56,547	34,227
Less valuation allowance	(56,545)	(34,227)
Total deferred tax assets, net of valuation allowance	2
Deferred tax liabilities:
Fixed assets	(2)
Total deferred tax liabilities	(2)
Net deferred tax asset	$ 0	$ 0