Liability for Pension and Other Retirement Benefits (Details 13) (Other Postretirement Benefit Plans, Defined Benefit [Member])	12 Months Ended
Mar. 31, 2011	Mar. 31, 2010	Mar. 31, 2009	Mar. 31, 2010
Weighted-average assumptions used to determine accumulated postretirement benefit obligations
Discount rate	5.60%			5.40%
Assumed rate of increase in future compensation levels	4.00%			4.00%
Current healthcare cost trend rate	7.90%			7.80%
Ultimate healthcare cost trend rate	4.80%			4.80%
Number of years to ultimate healthcare cost trend rate	5			7
Weighted average assumptions used to determine net periodic postretirement benefit cost
Discount rate	5.40%	6.40%	5.90%
Assumed rate of increase in future compensation levels	4.00%	4.00%	4.00%
Expected long-term rate of return on plan assets	5.60%	5.50%	5.50%
Current healthcare cost trend rate	7.80%	7.80%	7.70%
Ultimate healthcare cost trend rate	4.80%	4.80%	4.80%
Number of years to ultimate healthcare cost trend rate	7 years	7 years	6 years

Defined Benefit Plan Accumulated Current Healthcare Costs Trend Rate.

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Current healthcare cost trend rate.

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- Definition

Defined benefit plan assumptions used calculating benefit obligation rate of compensation increase point based Benefit system.

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Defined benefit plan assumptions used calculating net periodic benefit cost rate of compensation increase point based Benefit system.

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Number of years to ultimate healthcare cost trend rate.

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- Definition

Defined Benefit Plan Ultimate Health Care Costs Trend Rate.

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- Definition

The interest rate used to adjust for the time value of money for the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph j

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The interest rate used to adjust for the time value of money.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph j

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph j

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- Definition

The ultimate trend rate for health care costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph l

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- Definition

The year when the ultimate health care cost trend rate is expected to be reached.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph l

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