Income Taxes - Summary of Activity Related to Uncertain Tax Position (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Summary of activity related to uncertain tax positions
Balance at beginning of year	$ 69	$ 105
Decrease due to lapse of statute of limitations	0	(36)
Balance at end of year	$ 69	$ 69

Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319

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