Retirement Plans (Weighted-Average Asset Allocation for the Defined Benefit Cash Balance Plan) (Details)	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations	100.00%	100.00%
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations	36.00%	32.00%
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations	61.00%	64.00%
Other Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, actual plan asset allocations	3.00%	4.00%