The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 410
-SubTopic 20
-Name Accounting Standards Codification
-Section 25
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481999/410-20-25-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 410
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481850/410-20-50-1

Name:	us-gaap_AssetRetirementObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Asset Retirement Obligations - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Mar. 31, 2023	Sep. 30, 2023	Sep. 30, 2022
Asset Retirement Obligation [Line Items]
Change in asset retirement obligations		$ 73,739	$ 66,716
Ashpond and other
Asset Retirement Obligation [Line Items]
Change in asset retirement obligations	$ 10,900
Vogtle Unit Number 3
Asset Retirement Obligation [Line Items]
Cost to close plant	$ 62,800