Summary of Fair Value Estimates of Identifiable Intangible Assets and Weighted-Average Useful Lives (Detail) (USD $) In Thousands, unless otherwise specified			6 Months Ended
Sep. 30, 2013	Nov. 30, 2012	Sep. 30, 2013 Customer Relationships [Member]	Sep. 30, 2013 Sales contracts [Member]	Sep. 30, 2013 Permits [Member]
Business Acquisition [Line Items]
Weighted Average Life			15 years	4 years	40 years
Fair Value	$ 12,500	$ 12,500	$ 4,760	$ 2,500	$ 5,240

The amount of acquisition cost of a business combination allocated to an identifiable intangible asset that will be amortized.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph e

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 52

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_BusinessAcquisitionPurchasePriceAllocationAmortizableIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant