Other Postretirement Benefits (Components of Net Periodic Postretirement Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 0	$ 0	$ 0
Interest cost	66	88	80
Amortization of unrecognized prior service cost	14	15	14
Net periodic pension cost	$ 80	$ 103	$ 94
Discount rate	3.94%	3.74%	4.45%
Ultimate healthcare trend rates	4.00%
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 26	$ 16	$ 16
Interest cost	300	255	203
Amortization of unrecognized prior service cost	44	44	0
Loss amortization (2)	197	78	123
Net periodic pension cost	$ 567	$ 393	$ 342
Discount rate	3.90%	3.70%	4.50%
Annual rate of increase in the per capita cost of: Medical costs before age 65	7.80%	8.00%	8.50%
Annual rate of increase in the per capita cost of: Medical costs after age 65	6.80%	7.00%	7.30%
Annual rate of increase in the per capita cost of: Prescription drug costs	11.00%	9.00%	7.80%