Retirement plans (Details) - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Compensation and Retirement Disclosure [Abstract] | ||
| Maximum employer annual contribution per employee, percent | 4.50% | |
| Contributions to plan | $ 231,945 | $ 96,641 |
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- Definition The amount of the cost recognized during the period for defined contribution plans. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. No definition available.
|