Derivative Instruments and Hedging Activities - Notional principal amounts (Details) - Foreign currency forwards - USD ($) $ in Thousands	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Derivative Instruments and Hedging Activities
Unrealized loss	$ (300)	$ (300)
Instruments designated as accounting hedges:
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	169,095		$ 169,406
Instruments not designated as accounting hedges:
Derivative Instruments and Hedging Activities
Notional principal outstanding derivative instruments	24,824		27,909
Notional principal outstanding derivative instruments designed to manage exposure	$ 12,700		$ 14,700

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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- Details

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- Details

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- Details

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