Employee Benefit Plans and Postretirement Health Care and Life Insurance Benefits (Assumptions) Used (Details)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.20%	4.50%
Rate of compensation increase	2.50%	2.50%
Discount rate	4.50%	5.40%	5.50%
Expected return on plan assets	6.20%	7.10%	7.20%
Rate of compensation increase	2.50%	2.60%	2.90%
Other Post-Retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Discount rate	4.00%	4.30%
Discount rate	4.30%	5.10%	5.70%