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, 2017	Mar. 31, 2016
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	26.00%
Target Allocation Range, Minimum	16.00%
Target Allocation Range, Maximum	36.00%
Actual Allocation	31.90%	22.40%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	69.00%
Target Allocation Range, Minimum	59.00%
Target Allocation Range, Maximum	79.00%
Actual Allocation	61.70%	71.50%
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	5.00%
Target Allocation Range, Minimum	0.00%
Target Allocation Range, Maximum	10.00%
Actual Allocation	6.40%	6.10%