Contingencies and Legacy Environmental Commitments - Schedule of Environmental Activity (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Environmental Remediation Obligations [Abstract]
Environmental activity, Beginning balance	$ 12,684	$ 13,535	$ 14,293
Environmental costs incurred	(1,487)	(1,245)	(1,177)
Interest accretion	333	394	419
Reduction of environmental reserve-Wyoming Illinois	(1,207)
Environmental activity, Ending balance	$ 10,323	$ 12,684	$ 13,535

Non-cash reserve accretion

No definition available.

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- Definition

Amount of costs recognized in the balance sheet for known or estimated future costs arising from requirements to perform activities to remediate one or more sites.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 25

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=28360866&loc=d3e11660-110855

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- Definition

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 30

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859

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- Definition

Other increase (decrease) not attributable to current expense nor cash payments during an accounting period in estimated obligations recorded for probable future costs attributable to environmental contamination issues.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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