Selected Balance Sheet Data Selected Balance Sheet Data, Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Public Utilities, Inventory [Line Items]
Total inventories	$ 512	$ 544
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	275	270
Fuel
Public Utilities, Inventory [Line Items]
Inventories	157	191
Natural gas
Public Utilities, Inventory [Line Items]
Inventories	$ 80	$ 83

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_InventoryNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The period end amount for a type of inventory held by the utility in a schedule of inventories.

+ References

Reference 1: 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(6)(a))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_PublicUtilitiesInventory
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

Name:	us-gaap_PublicUtilitiesInventoryLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PublicUtilitiesInventoryAxis=us-gaap_PublicUtilitiesInventorySuppliesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesInventoryAxis=us-gaap_PublicUtilitiesInventoryFuelMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesInventoryAxis=us-gaap_PublicUtilitiesInventoryNaturalGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: