Retirement and Share-based Compensation Plans (Deferred Compensation Arrangements) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Plans, Certain Officers, Directors and Consultants [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Shares earned and reserved for future issuance	364,000	364,000
Share-based compensation expense			$ 102,000
Deferred Compensation Plans, Officer Rabbi Trust [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Deferred compensation liability	$ 2,000,000	$ 3,500,000
Shares held	34,539	102,932