Contingencies and Legacy Environmental Commitments - Schedule of Environmental Activity (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014
Environmental Remediation Obligations [Abstract]
Environmental activity, Beginning balance	$ 10,323
Environmental costs incurred	(383)	(602)	(1,487)
Interest accretion	149	174
Reduction of environmental reserve-Part of Federal Labs site subject to the 2001 Consent Order	(412)
Environmental activity, Ending balance	$ 9,677		$ 10,323

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

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration