Retirement and Deferred Compensation Plan - Deferred Compensation Plan (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accrued bonus and deferred compensation	$ 41,508	$ 36,753
Deferred Compensation Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Deferred compensation plan assets	1,600	1,100
Accrued bonus and deferred compensation	4,600	3,800
Employer contribution to deferred compensation plan	$ 200	$ 300	$ 200

Amount of contributions made by employer into fund established for purposes of making future disbursement to individual in accordance with deferred compensation arrangement.

No definition available.

+ Details

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

+ References

No definition available.

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- Definition

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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