Revolving Line of Credit - Additional Information (Detail)	12 Months Ended
Sep. 30, 2016 USD ($)	Nov. 30, 2014 USD ($)
Line of Credit Facility [Line Items]
Unsecured revolving line of credit	$ 400,000,000	$ 200,000,000
Revolving credit facility, expiration date	Dec. 30, 2019
Credit facility restrictive covenant, minimum fixed charge ratio	2.5
Credit facility restrictive covenant, maximum consolidated leverage ratio	3.0
Credit facility restrictive covenant, maximum consolidated leverage ratio step up	3.5
Borrowings outstanding	$ 255,000,000
Interest rate of borrowings outstanding	1.661%
Long-term debt
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 250,000,000
Federal Fund Rate
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.50%
LIBOR
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.00%
LIBOR \| Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.00%
LIBOR \| Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	1.875%
Base Rate \| Minimum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.00%
Base Rate \| Maximum
Line of Credit Facility [Line Items]
Debt instrument basis spread on variable rate	0.875%

Fixed Charge Coverage Ratio, Minimum

No definition available.

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- Definition

Leverage Ratio Maximum

+ References

No definition available.

+ Details

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- Definition

Leverage Ratios, Step Up, Maximum

+ References

No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 19, 20, 22
-Article 5

+ Details

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- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ 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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

The effective interest rate at the end of the reporting period.

+ References

+ 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

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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