Annual report pursuant to Section 13 and 15(d)

Benefit Plans and Collective Bargaining Agreements Defined Contribution Plans (Details)

v3.8.0.1
Benefit Plans and Collective Bargaining Agreements Defined Contribution Plans (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
401(k) Employee Stock Ownership Plan [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Defined Contribution Plan, Cost Recognized $ 608,473 $ 516,991 $ 541,260
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent 100.00%    
Defined Contribution Plan, Employer Discretionary Contribution Amount $ 0 $ 0 $ 0
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Amount Under Economic Growth and Tax Relief Reconciliation Act $ 24,000    
Defined Contribution Plan, Employer Matching Contribution, Percent of Match 100.00%    
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay 4.00% 4.00% 4.00%
Defined Contribution Plan, Additional Annual Contribution Per Employee, Amount Under Economic Growth and Tax Relief Reconciliation Act $ 6,000    
Defined Contribution Plan, Additional Annual Contribution Per Employee, Minimum Age Under Economic Growth and Tax Relief Reconciliation Act 50 years    
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount $ 18,000    
401(k) and Profit Sharing Plan [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Defined Contribution Plan, Cost Recognized $ 174,229 $ 136,763 $ 147,005
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent 60.00%    
Defined Contribution Plan, Employer Discretionary Contribution Amount $ 0 $ 0 $ 0
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Amount Under Economic Growth and Tax Relief Reconciliation Act 24,000    
Defined Contribution Plan, Additional Annual Contribution Per Employee, Amount Under Economic Growth and Tax Relief Reconciliation Act $ 6,000    
Defined Contribution Plan, Additional Annual Contribution Per Employee, Minimum Age Under Economic Growth and Tax Relief Reconciliation Act 50 years    
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount $ 18,000    
Maximum [Member] | Other Pension Plan, Postretirement or Supplemental Plans [Member]      
Defined Contribution Plan Disclosure [Line Items]      
Defined Benefit Plan, Funded Percentage 80.00%    
Defined Benefit Plan, Employer Contribution Percent of Eligible Compensation 3.75%    
Defined Benefit Plan, Employer Contribution as Percent of Total Contributions 5.00%    
Defined Benefit Plan, Contributions by Employer $ 69,245