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Benefit Plans Postretirement Benefit Costs Deferred as Regulatory Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure
Regulatory assets	$ (7,956)	$ (10,245)
Non-current regulatory liabilities	40	23
Pension Benefits
Defined Benefit Plan Disclosure
Unrecognized prior service cost (credit)	(517)	(615)
Unrecognized net loss	4,062	5,620
Amount capitalized due to actions of regulator	(91)	(110)
Regulatory assets	(3,636)	(5,115)
Other Post-retirement Benefits
Defined Benefit Plan Disclosure
Unrecognized prior service cost (credit)	(93)	(112)
Unrecognized net loss	125	190
Amount capitalized due to actions of regulator	0	0
Regulatory assets	(32)	$ (78)
Non-current regulatory liabilities	$ 32

X

- Definition

Amount deferred as regulatory asset of gains and losses that are not yet recognized as a component of net periodic benefit cost. Gains and losses are due to changes in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan.

+ References

No definition available.

+ Details

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X

- Definition

Deferred amount in regulatory assets related to the cost of benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation, which has not yet been recognized as components of net periodic benefit cost.

+ References

No definition available.

+ Details

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X

- Definition

Defined benefit plan amounts deferred as regulatory assets due to actions by regulators

+ References

No definition available.

+ 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

Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

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X

- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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