Stock-Based Compensation - Narrative (Details)	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Unvested options were exercisable at an average | $ / shares	$ 8.02
Stock options
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Additional stock-based compensation | $	$ 162,000
Stock-based compensation expense related to unvested options not yet recognized | $	$ 98,000
Chief Executive Officer | Stock options
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Accelerated vesting of unvested stock options | shares	258,334
Chief Financial Officer | Stock options
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Accelerated vesting of unvested stock options | shares	71,667