Income Taxes - Gross Unrecognized Income Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Taxes
Gross unrecognized income tax benefits at beginning of year	$ 5,002	$ 4,497	$ 4,552
Changes based on tax positions related to the current year	122	25
Increases for tax positions related to prior years	1,437	1,055
Settlements	(417)
Lapse of statute of limitations	(3,082)	(575)	(55)
Gross unrecognized income tax benefits at end of year	3,062	5,002	4,497
Accrued liabilities for interest and penalties	(1,800)	$ (200)	$ 100
Interest and penalties accrued	700
Unrecognized tax benefits that would impact effective tax rate	$ 2,800

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- Definition

The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319

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- Definition

The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.

+ References

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

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- Definition

Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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- Definition

Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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