Marketable Securities - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended
Jun. 30, 2013	Sep. 30, 2012
Marketable Securities [Abstract]
Net unrealized gains/losses	$ 1,282,000	$ 807,000
Estimated interest accrued	421,000	545,000
Transfers of investments between Level 1 and Level 2	$ 0	$ 0

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

Name:	us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant