Benefit Plans (Significant Actuarial Assumptions Used to Determine Net Periodic Pension Costs) (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Actuarial assumptions used in calculations
Weighted average assumed discount rate		4.27%	5.10%	4.25%
Weighted average expected long-term rate of return on plan assets	7.00%	7.50%	7.75%	8.00%
Assumed long-term rate of annual compensation increases		4.50%	5.00%	4.50%