Notes Payable and Long-Term Debt (Short-Term Debt) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Short-term Debt [Line Items]
Short-term notes payable and current portion of long-term debt	$ 1,800,000	$ 857,000
Notes Payable to Banks [Member] | Unsecured Debt [Member]
Short-term Debt [Line Items]
Interest rate description	WSJ	WSJ
Basis spread on variable rate	0.50%	1.00%
Notes Payable to Banks [Member] | Unsecured Debt [Member] | Notes due March 2017 [Member]
Short-term Debt [Line Items]
Short-term notes payable and current portion of long-term debt	$ 1,800,000	$ 0
Current borrowing capacity	1,000,000
Notes Payable to Banks [Member] | Unsecured Debt [Member] | Notes due November 2015 [Member]
Short-term Debt [Line Items]
Short-term notes payable and current portion of long-term debt	0	857,000
Current borrowing capacity	800,000
Line of Credit [Member] | Secured Debt [Member]
Short-term Debt [Line Items]
Short-term notes payable and current portion of long-term debt	0	$ 0
Current borrowing capacity	$ 1,000,000
Interest rate description	WSJ
Basis spread on variable rate	4.50%