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Benefit Plans Components of Benefit Plans (Details) - USD ($)	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan Disclosure
Fixed and variable fund annual maximum contribution	$ 10,000
Defined contribution plan contribution amount	$ 105,000,000	$ 97,000,000	$ 92,000,000
Minimum
Defined Benefit Plan Disclosure
Threshold for Deferral of Actuarial Gain/Loss Under Corridor Approach	10.00%

X

- Definition

The maximum annual contribution that employees can make to the fixed and variable fund benefit. The fixed fund benefit is a benefit that earns a specified rate of interest on contributions made by employees. The variable fund is a benefit that invests employee contributions in the Spartan U.S. Equity Index Fund-Fidelity Advantage Class (Spartan).

+ References

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- Definition

Threshold for Deferral of Actuarial Gain/Loss Under Corridor Approach

+ References

No definition available.

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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.

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No definition available.

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480794/715-70-50-1

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