Annual report pursuant to Section 13 and 15(d)

Defined Contribution Plan (Details Textual)

Defined Contribution Plan (Details Textual) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]    
Description of Defined Contribution Pension and Other Postretirement Plans Participants may contribute up to 100% of their total compensation to the Plan, not to exceed the limit as defined in the Code.  
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay 50.00%  
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent 6.00%  
Defined Contribution Plan, Employer Discretionary Contribution Amount $ 97,000 $ 105,000