Retirement Plans and Profit Sharing Arrangements (Weighted Average Assumptions) (Details 5)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Plans [Member]
Weighted average assumptions used to determine benefit obligations for pension plans
Discount rates (as a percent)	3.32%	3.66%
Rates of increase in compensation levels (as a percent)	4.29%	4.39%
Weighted average assumptions used to determine net periodic benefit cost for pension plans
Discount rates (as a percent)	3.64%	3.67%	3.43%
Rates of increase in compensation levels (as a percent)	4.39%	4.43%	4.41%
Expected long term rates of return on assets (as a percent)	7.13%	6.98%	7.10%
Other Postretirement Benefits Plan [Member]
Weighted average assumptions used to determine benefit obligations for pension plans
Discount rates (as a percent)	3.41%	3.77%