Nature of Operations - Additional Information (Detail)	12 Months Ended
Aug. 31, 2012 Segment Vehicle
Organization and Nature of Operations [Line Items]
Number of business segments	3
Number of railcars owned	11,000
Number of railcars that get services	219,000

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration