CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 272,171	$ 271,674	$ 256,996
Other comprehensive loss, net of tax
Loss on interest rate swaps	(1,484)	(1,527)	0
Other comprehensive loss	(1,484)	(1,527)	0
Total comprehensive income	$ 270,687	$ 270,147	$ 256,996

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the economic entity, including both controlling (parent) and noncontrolling interests. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, including any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

+ References+ Details

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Other Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6519514

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

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Reference 11: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 87-21

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Net Income

-URI http://asc.fasb.org/extlink&oid=6518256

Reference 13: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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Reference 14: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

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Reference 15: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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Reference 16: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 20

-Article 9

+ Details

- Definition

Net of tax effect change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges, that is attributable to the parent entity. The change includes an entity's share of an equity investee's increase (decrease) in deferred hedging gains or losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-URI http://asc.fasb.org/extlink&oid=6921930&loc=SL4573702-111684

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

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+ Details

- Definition

This element represents Other Comprehensive Income or Loss, Net of Tax, for the period. Includes deferred gains or losses on qualifying hedges, unrealized holding gains or losses on available-for-sale securities, minimum pension liability, and cumulative translation adjustment. While for technical reasons this element has no balance attribute, the default assumption is a credit balance consistent with its label.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 22, 23, 24, 25

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

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-Publisher SEC

-Name Regulation S-X (SX)

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+ Details