Components of Net Periodic Benefit Cost (Benefit Cost (Increase)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	$ 0	$ 0
Interest cost	274	307
Expected return on plan assets	(693)	(638)
Amortization of prior service cost	0	0
Amortization of net loss (gain)	199	230
Net periodic benefit (increase) cost	(220)	(101)
Other post-retirement benefits [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	29	26
Interest cost	197	218
Expected return on plan assets	0	0
Amortization of prior service cost	0	0
Amortization of net loss (gain)	(99)	(169)
Net periodic benefit (increase) cost	$ 127	$ 75