Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Net operating loss carryforward	$ 12,286	$ 6,336
Intangible assets	38	41
Accrued expense	335	184
Stock-based compensation	283	112
Other	76	36
Total deferred tax assets	16,713	7,333
Deferred tax liabilities
Depreciable assets	(60)	(49)
Total deferred tax liabilities	(60)	(49)
Less: Valuation allowance	(16,653)	(7,284)
Deferred tax assets, net	0	0
Federal
Deferred tax assets
Tax credits	3,291	$ 624
State
Deferred tax assets
Tax credits	$ 404