Employee Benefit Plans (Weighted Assumptions) (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
RELS Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate	3.97%	4.44%	4.09%
Discount rate		3.97%
Expected return on plan assets		3.50%
SERPs
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate	4.00%	4.20%	3.85%
Discount rate	3.50%	4.00%
Restoration Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average discount rate	4.08%	4.32%	3.98%
Discount rate	3.57%	4.08%