Leases - Summary of future minimum lease payments (prior period) (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Future Minimum Lease Payments [Line Items]
Remainder	$ 918
2019	3,653
2020	2,958
2021	2,958
2022	2,958
2023 and thereafter	17,641
Total future minimum lease payments (undiscounted)	$ 31,086
Prior Period [Member]
Future Minimum Lease Payments [Line Items]
Remainder		$ 921
2019		3,764
2020		3,516
2021		3,146
2022		2,958
2023 and thereafter		20,599
Total future minimum lease payments (undiscounted)		$ 34,904

Amount of lessee's undiscounted obligation for lease payments for operating lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due after fifth fiscal year following latest fiscal year.

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fifth fiscal year following latest fiscal year.

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fourth fiscal year following latest fiscal year.

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in third fiscal year following latest fiscal year.

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in second fiscal year following latest fiscal year.

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease having an initial or remaining lease term in excess of one year due in remainder of fiscal year following latest fiscal year.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980

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- Definition

Future Minimum Lease Payments [Line Items]

+ References

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