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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, 2012
Mar. 31, 2011
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation, Total 100.00%  
Actual Allocation, Total 100.00% 100.00%
Domestic Equity Securities [Member]
   
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation, Equity securities 44.00%  
Target Allocation Range, Equity securities, Minimum 37.00%  
Actual Allocation, Equity securities 45.50% 45.60%
International Equity Securities [Member]
   
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation, Equity securities 13.00%  
Target Allocation Range, Equity securities, Minimum 10.00%  
Target Allocation Range, Equity securities, Maximum 16.00%  
Actual Allocation, Fixed income securities 12.10% 13.60%
Fixed Income Securities [Member]
   
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation, Fixed income securities 33.00%  
Target Allocation Range, Fixed Income securities, Minimum 26.00%  
Target Allocation Range, Fixed Income securities, Maximum 40.00%  
Actual Allocation, Fixed income securities 32.30% 31.20%
Real Estate Funds [Member]
   
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation, Real estate funds 5.00%  
Target Allocation Range, Real estate funds, Minimum 3.00%  
Target Allocation Range, Real estate funds, Maximum 7.00%  
Actual Allocation, Real estate funds 5.40% 4.70%
Hedge Funds [Member]
   
Defined Benefit Plan Disclosure [Line Items]    
Target Allocation, Hedge funds 5.00%  
Target Allocation Range, Hedge funds, Minimum 3.00%  
Target Allocation Range, Hedge funds, Maximum 7.00%  
Actual Allocation, Hedge funds 4.70% 4.90%