Acquisitions, Development and Divestitures - Development (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Jun. 30, 2022	Dec. 31, 2022
Business Acquisition [Line Items]
Income (Loss) from Discontinued Operations (net of income taxes)		$ 0
Transition Service Agreement Cost	$ 58
Goodwill	2,248			$ 2,248
Operating Revenues from external customers	2,415	1,782
Net income (loss)	285	273
Indemnification for Safari sale/leaseback	25
Narragansett Electric
Business Acquisition [Line Items]
Total cash consideration			$ 3,800
Rhode Island Regulated
Business Acquisition [Line Items]
Operating Revenues from external customers	565	0
Net income (loss)	54	0
Corporate and Other [Member]
Business Acquisition [Line Items]
Operating Revenues from external customers	(1)	3
Net income (loss)	(73)	$ (59)
Rhode Island Energy | Rhode Island Energy TSA
Business Acquisition [Line Items]
Other Nonrecurring (Income) Expense	54
Rhode Island Energy | Accrual for TSA Markup
Business Acquisition [Line Items]
Other Nonrecurring (Income) Expense	$ 2