Employee Defined Contribution Plan

12 Months Ended

Dec. 31, 2017

Compensation And Retirement Disclosure [Abstract]

Employee defined contribution plan

15. Employee defined contribution plan

Full time employees of the Group in the PRC participate in a government mandated defined contribution plan, pursuant to which certain pension benefits, medical care, employee housing fund and other welfare benefits are provided to employees. Chinese labor regulations require that the Group's PRC subsidiary make contributions to the government for these benefits based on certain percentages of the employees' salaries. The Group has no legal obligation for the benefits beyond the contributions made. The total amounts for such employee benefits, which were expensed as incurred, were $79,878, $288,666 and $579,094 for the years ended December 31, 2015, 2016 and 2017, respectively.