Inventories (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Public Utilities, Inventory [Line Items]
Inventories	$ 253	$ 295
Materials and supplies
Public Utilities, Inventory [Line Items]
Inventories	181	178
Fuel
Public Utilities, Inventory [Line Items]
Inventories	66	90
Natural Gas
Public Utilities, Inventory [Line Items]
Inventories	$ 6	$ 27

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

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

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