Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Provision or benefit from income taxes	$ 0	$ 0	$ 0
Increase in valuation allowance	9,400,000	3,900,000	$ 3,000,000
Net operating loss carryforwards	36,100,000	18,600,000
Unrecognized tax benefit	0
Federal
Income Taxes [Line Items]
Tax credit carryforwards	3,300,000	624,000
State
Income Taxes [Line Items]
Tax credit carryforwards	$ 612,000	$ 0
Earliest Tax Year
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year	2033
Tax credit carryforwards, expiration year	2033