Derivative Instruments and Hedging Activities - Notional principal amounts (Details) - Foreign currency forwards - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments and Hedging Activities
Unrealized gain (loss) on derivative	$ 100	$ 8,200
Instruments designated as accounting hedges:
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	125,486	158,664
Instruments not designated as accounting hedges:
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	35,117	115,070
Notional principal outstanding derivative instruments designed to manage exposure	$ 18,500	$ 78,400

Aggregate notional amount specified by the derivative(s) designed to manage exposure. Expressed as an absolute value.

No definition available.

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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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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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

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- Details

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- Details

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- Details

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