Fair Value Measurements - Recurring Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Liabilities
Restricted cash	$ 54	$ 49
Recurring
Assets
Fair value, assets	847	1,837
Liabilities
Fair value, liabilities	(5)	(1)
Net assets	842	1,836
Recurring \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	(5)	(1)
Recurring \| FTRs \| Derivative Assets
Assets
Fair value, assets	12	9
Recurring \| Equity securities
Assets
Fair value, assets	2	2
Recurring \| U.S. state debt securities
Assets
Fair value, assets	263	273
Recurring \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	532	1,511
Recurring \| Other
Assets
Fair value, assets	38	42
Recurring \| Level 1
Assets
Fair value, assets	534	1,513
Liabilities
Fair value, liabilities	0	0
Net assets	534	1,513
Recurring \| Level 1 \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Recurring \| Level 1 \| FTRs \| Derivative Assets
Assets
Fair value, assets	0	0
Recurring \| Level 1 \| Equity securities
Assets
Fair value, assets	2	2
Recurring \| Level 1 \| U.S. state debt securities
Assets
Fair value, assets	0	0
Recurring \| Level 1 \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	532	1,511
Recurring \| Level 1 \| Other
Assets
Fair value, assets	0	0
Recurring \| Level 2
Assets
Fair value, assets	301	315
Liabilities
Fair value, liabilities	0	0
Net assets	301	315
Recurring \| Level 2 \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	0	0
Recurring \| Level 2 \| FTRs \| Derivative Assets
Assets
Fair value, assets	0	0
Recurring \| Level 2 \| Equity securities
Assets
Fair value, assets	0	0
Recurring \| Level 2 \| U.S. state debt securities
Assets
Fair value, assets	263	273
Recurring \| Level 2 \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	0	0
Recurring \| Level 2 \| Other
Assets
Fair value, assets	38	42
Recurring \| Level 3
Assets
Fair value, assets	12	9
Liabilities
Fair value, liabilities	(5)	(1)
Net assets	7	8
Recurring \| Level 3 \| FTRs \| Derivative Liabilities
Liabilities
Fair value, liabilities	(5)	(1)
Recurring \| Level 3 \| FTRs \| Derivative Assets
Assets
Fair value, assets	12	9
Recurring \| Level 3 \| Equity securities
Assets
Fair value, assets	0	0
Recurring \| Level 3 \| U.S. state debt securities
Assets
Fair value, assets	0	0
Recurring \| Level 3 \| Cash, cash equivalents and restricted cash
Assets
Fair value, assets	0	0
Recurring \| Level 3 \| Other
Assets
Fair value, assets	$ 0	$ 0

Fair value of assets and liabilities net.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

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Fair value of financial and nonfinancial obligations.

+ References

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- Definition

Amount of cash restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126999549&loc=SL98516268-108586

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(1))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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