Retirement Plans (Weighted-average rate assumptions of the Pension and Postretirement Plans) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate used in determining benefit obligation — December 31	4.22%	4.55%	4.15%
Discount rate used in determining expense	4.55%	4.15%	5.00%
Expected long-term return on Pension Plan assets	6.75%	6.75%	7.00%
Rate of compensation increase used in determining benefit obligation — December 31	3.50%	3.50%	3.50%
Rate of compensation increase used in determining pension expense	3.50%	3.50%	3.50%
Year 1 increase in cost of postretirement benefits	0.00%	0.00%	0.00%
Postretirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate used in determining benefit obligation — December 31	3.79%	4.23%	3.75%
Discount rate used in determining expense	4.23%	3.75%	4.27%
Expected long-term return on Pension Plan assets	0.00%	0.00%	0.00%
Rate of compensation increase used in determining benefit obligation — December 31	0.00%	0.00%	0.00%
Rate of compensation increase used in determining pension expense	0.00%	0.00%	0.00%
Year 1 increase in cost of postretirement benefits	7.00%	7.50%	8.00%