Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012
Commitments And Contingencies [Line Items]
Unapproved change orders	$ 9.4	$ 8.5

The amount of costs incurred on unapproved change orders when it is probable that the cost will be recovered through a change in the contract price.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Subparagraph c(3)

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 910

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6471523&loc=d3e50000-109363

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 910

-SubTopic 310

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6471494&loc=d3e49324-109356

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