Significant Accounting Policies (Detail Textuals 1) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Depreciation method used for property, plant and equipment	straight-line basis
Goodwill	$ 32,150,000	$ 32,150,000
Advertising expenses	$ 1,696,000	$ 1,296,000	$ 2,058,000
Statutory federal income tax rate	35.00%	35.00%	35.00%
Corporate income tax rate effective in 2018	21.00%
Discrete tax benefit adjustment	$ 19,300,000
Defined Benefit Pension Plan
Significant Accounting Policies [Line Items]
Defined benefit pension plan eligibility criteria	defined benefit pension plan that provides monthly benefits upon retirement at age 65 to eligible employees with at least one year of service prior to 2002
Operating equipment | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	3 Years
Operating equipment | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	20 years
Buildings and leasehold improvements | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	15 Years
Buildings and leasehold improvements | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	39 years
Furniture and fixtures | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	5 Years
Furniture and fixtures | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	7 years
Software
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	5 years
Vehicles | Minimum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	3 Years
Vehicles | Maximum
Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	5 years