Postretirement Benefit Plans (Net Periodic Benefit (Income) Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Postretirement Health And Life Coverage [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	$ 4	$ 4	$ 13
Interest Cost	20	23	32
Amortization of prior service cost	(35)	(35)
Net periodic postretirement benefit (income) cost	(11)	(8)	45
Director's Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service Cost	35	34	33
Interest Cost	43	46	45
Amortization of prior service cost	22	22	22
Net periodic postretirement benefit (income) cost	$ 100	$ 102	$ 100