Defined Contribution Plan	12 Months Ended
Defined Contribution Plan	Dec. 31, 2017
Defined Contribution Plan
Defined Contribution Plan	13. Defined Contribution Plan The Company established a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax basis. Company contributions to the plan may be made at the discretion of the board of directors. Effective September 1, 2017, the Company instituted an employer match of 100% of the amount you contribute to the Plan for each payroll period up to the first 1% of Plan Compensation plus 50% of the amount you contribute between 1% and 6% of Plan Compensation. For the year ended December 31, 2017, the Company contributed $0.3 million to the 401(k) Plan.