Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 553,690	$ 632,045	$ 642,889
Ending Balance	607,644	553,690	632,045
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	15,166	5,898	15,687
Other comprehensive (loss) income before reclassifications	283	8,291	(9,887)
Amounts reclassified from accumulated other comprehensive income	(236)	977	98
Ending Balance	15,213	15,166	5,898
Currency Translation Adjustments
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	15,389	6,545	16,102
Other comprehensive (loss) income before reclassifications	(221)	8,844	(9,426)
Amounts reclassified from accumulated other comprehensive income			(131)
Ending Balance	15,168	15,389	6,545
Unrealized Gains (Losses) on Available-for-Sale Securities
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(3)	103	(38)
Other comprehensive (loss) income before reclassifications	(10)	(231)	144
Amounts reclassified from accumulated other comprehensive income	12	125	(3)
Ending Balance	(1)	(3)	103
Pension Liability Adjustments
Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(220)	(750)	(377)
Other comprehensive (loss) income before reclassifications	514	(322)	(605)
Amounts reclassified from accumulated other comprehensive income	(248)	852	232
Ending Balance	$ 46	$ (220)	$ (750)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount after tax, before reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66004921&loc=d3e1436-108581

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-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669686-108580

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- Definition

Amount after tax of reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669686-108580

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- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 55
-Paragraph 4I
-URI http://asc.fasb.org/extlink&oid=65897068&loc=SL4590271-111686

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