Retirement Plans, Weighted Average Assumptions used to Determine Benefit and Net Periodic Benefit Costs (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Expected long-term rate of return on plan assets	5.93%	6.50%
Retirement Account Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.30%	3.70%
Rate of increase in compensation levels	3.00%	3.00%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.77%	4.10%
Rate of increase in compensation levels	3.00%	4.00%
Expected long-term rate of return on plan assets	5.93%	6.50%
Postretirement Plan
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.30%	3.70%
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.77%	4.10%
Retirement Account Plan Prior to Merger [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.70%
Expected long-term rate of return on plan assets	6.00%
Other Pension Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.00%
Expected long-term rate of return on plan assets	5.50%