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, 2013	Mar. 31, 2012
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	44.00%
Target Allocation Range, Minimum	37.00%
Target Allocation Range, Maximum	51.00%
Actual Allocation	44.30%	45.50%
International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	13.00%
Target Allocation Range, Minimum	10.00%
Target Allocation Range, Maximum	16.00%
Actual Allocation	12.70%	12.10%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	33.00%
Target Allocation Range, Minimum	26.00%
Target Allocation Range, Maximum	40.00%
Actual Allocation	32.60%	32.30%
Real Estate Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	5.00%
Target Allocation Range, Minimum	3.00%
Target Allocation Range, Maximum	7.00%
Actual Allocation	5.60%	5.40%
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	5.00%
Target Allocation Range, Minimum	3.00%
Target Allocation Range, Maximum	7.00%
Actual Allocation	4.80%	4.70%