Contingencies and Legacy Environmental Commitments - Schedule of Environmental Activity (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2013
Environmental Remediation Obligations [Abstract]
Environmental activity, Beginning balance	$ 12,684
Environmental costs incurred	(1,039)	(939)	(1,245)
Interest accretion	256	299
Reduction of environmental reserve-Wyoming Illinois	(1,207)
Environmental activity, Ending balance	$ 10,694		$ 12,684

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

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