Retirement Plans (Weighted Average Asset Allocations, By Asset Category) (Details)	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocation (in hundredths)	100.00%	100.00%
Equity [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocation (in hundredths)	49.00%	48.00%
Debt Securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocation (in hundredths)	39.00%	40.00%
Alternative Investments [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocation (in hundredths)	12.00%	12.00%