Postretirement Benefit Plans (Employer Contributions to Plans) (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Contributions to employee benefit plans
Funded pension plans	$ 26	$ 28	$ 28
Unfunded pension plans	15	12	13
Savings and defined contribution pension plans	25	24	18
Total contributions	$ 66	$ 64	$ 59

Defined contribution plan employers contribution.

No definition available.

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- Definition

Defined contribution plan employers contribution to funded pension plan.

+ References

No definition available.

+ Details

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- Definition

Defined contribution plan employers contribution to savings and defined contribution pension plan.

+ References

No definition available.

+ Details

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- Definition

Defined contribution plan employer's contribution to unfunded pension plan.

+ References

No definition available.

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- Definition

The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and its non-pension postretirement benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3536-108585

+ Details

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