Pension And Other Postretirement Benefit Plans (Weighted-Average Target Pension Asset Allocation And Target Ranges By Major Asset Category) (Details)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%
Actual Allocation	100.00%	100.00%
Domestic Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	29.00%
Actual Allocation	27.40%	31.90%
Domestic Equity Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.19
Domestic Equity Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.39
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	66.00%
Actual Allocation	65.90%	61.70%
Fixed Income Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.56
Fixed Income Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.76
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	5.00%
Actual Allocation	6.70%	6.40%
Real Estate Funds [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0
Real Estate Funds [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.1