Pension And Other Postretirement Benefit Plans (Assumptions Used To Compute Net Periodic Benefit Cost And Benefit Obligations) (Details)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Healthcare cost trend rate	7.60%
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate: Benefit cost for plan year	4.60%	5.50%	6.00%
Discount rate: Benefit obligation at end of plan year	4.20%	4.60%	5.50%
Expected long-term return on plan assets: Benefit cost for plan year	8.00%	8.00%	8.00%
Expected long-term return on plan assets: Benefit obligation at end of plan year	8.00%	8.00%	8.00%
Salary scale	5.00%	5.00%	5.00%
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate: Benefit cost for plan year	4.40%	5.50%	6.00%
Discount rate: Benefit obligation at end of plan year	3.90%	4.40%	5.50%
Expected long-term return on plan assets: Benefit cost for plan year	4.30%	4.30%	4.30%
Expected long-term return on plan assets: Benefit obligation at end of plan year	4.30%	4.30%	4.30%
Salary scale	5.00%	5.00%	5.00%
Healthcare cost trend rate	7.60%	7.80%	8.00%