Pension And Other Postretirement Benefit Plans (Assumptions Used To Compute Net Periodic Benefit Cost And Benefit Obligations) (Details)	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Healthcare cost trend rate	7.00%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates: Benefit cost for plan year	3.80%	4.50%	4.20%
Discount rates: Benefit obligation at end of plan year	4.10%	3.80%	4.50%
Expected long-term return on plan assets: Benefit cost for plan year	7.25%	7.75%	8.00%
Expected long-term return on plan assets: Benefit obligation at end of plan year	7.00%	7.25%	7.75%
Salary scale: Benefit cost for plan year	4.50%	4.50%	5.00%
Salary scale: Benefit obligation at end of plan year	4.00%	4.50%	4.50%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rates: Benefit cost for plan year	3.70%	4.30%	3.90%
Discount rates: Benefit obligation at end of plan year	3.80%	3.70%	4.30%
Expected long-term return on plan assets: Benefit cost for plan year	3.00%	4.30%	4.30%
Expected long-term return on plan assets: Benefit obligation at end of plan year	3.00%	3.00%	4.30%
Salary scale: Benefit cost for plan year	4.50%	4.50%	5.00%
Salary scale: Benefit obligation at end of plan year	4.00%	4.50%	4.50%
Healthcare cost trend rate	7.00%	7.20%	7.40%