Acquisitions, Development and Divestitures - Development (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended		18 Months Ended	25 Months Ended
	May 25, 2022	Jun. 30, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2024	Dec. 31, 2021
Business Acquisition [Line Items]
Business Combination, Integration Related Costs			$ 74.0		$ 101.0	$ 10.0
Aggregate enterprise consideration			5,300.0
Less: fair value of assumed long-term debt outstanding, net		$ 1,500.0	1,500.0		1,500.0		$ 1,500.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, AR Reserve	$ 60.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables, Gross	255.0
Business Combination, Transaction Costs Expense					18.0
Goodwill, Acquired During Period			1,581.0
Total cash consideration					3,800.0
Operating Revenues Pro Forma					4,203.0	3,588.0
Income (Loss) from Discontinued Operations (net of income taxes)				$ 555.0	0.0	(1,488.0)
Net Income (Loss) Pro Forma					456.0	(259.0)
Transition Service Agreement Cost			18.0		18.0
Goodwill		2,297.0	2,297.0		2,297.0		2,297.0		$ 716.0
Operating Revenues from external customers			1,696.0	1,288.0	3,478.0	2,786.0
Net income (loss)			119.0	19.0	392.0	(1,821.0)
Transaction Costs | Additional Costs Related to Purchase
Business Acquisition [Line Items]
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized							27.0
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses | Transaction Costs | Additional Costs Related to Purchase
Business Acquisition [Line Items]
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized			16.0		18.0
Rhode Island Regulated
Business Acquisition [Line Items]
Goodwill		725.0	725.0		725.0		$ 725.0
Operating Revenues from external customers			128.0	0.0	128.0	0.0
Net income (loss)			(29.0)	0.0	(29.0)	0.0
Corporate and Other [Member]
Business Acquisition [Line Items]
Goodwill, Purchase Accounting Adjustments			856.0
Operating Revenues from external customers			9.0	10.0	12.0	18.0
Net income (loss)			(78.0)	$ (716.0)	(127.0)	$ (772.0)
Rhode Island Energy
Business Acquisition [Line Items]
Business Combination, Regulatory Assets	75.0
Public Utilities, Customer Bill Credit Agreement, Total	50.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	195.0
RICCREF Contribution Expense			2.5
Business Acquisition, Unbilled Revenues	54.0
Total Current Assets	630.0
Business Combination, Price Risk Management Assets	99.0
Property, Plant and Equipment, net	3,990.0
Regulatory Assets	437.0
Goodwill	1,581.0
Other Noncurrent Assets	134.0
Total Noncurrent Assets	6,142.0
Accounts Receivable Forgiven, net		21.0
Total Assets	6,772.0
Business Combination, Regulatory Assets Expensed			20.0		20.0
Long-Term Debt Due Within One Year	14.0
Acquisition commitment write off expenses					48.0
Accounts Receivable Forgiven, AR Reserve			23.0		23.0
Accounts Payable	183.0
Less: fair value of assumed long-term debt outstanding, net	1,496.0
Taxes Accrued	44.0
Regulatory Liabilities	237.0
Other Current Liabilities	198.0
Regulatory Liabilities	628.0
Other Deferred Credits and Noncurrent Liabilities	150.0
Noncurrent Liabilities	2,274.0
Total cash consideration		3,822.0
Cash and cash equivalents	142.0
Other Current Assets	65.0
Total Current Liabilities	676.0
Accounts Receivable Forgiven, Gross		$ 44.0
Operating Revenues from external customers					128.0
Net income (loss)					(29.0)
Rhode Island Energy | Accounts Receivable and Regulatory Asset write off
Business Acquisition [Line Items]
Acquisition commitment write off expenses					43.0
Rhode Island Energy | Accrued expenditures for the RIAG and decarbonation goals
Business Acquisition [Line Items]
Acquisition commitment write off expenses					$ 5.0
Rhode Island Energy | Accrual for RIAG Evaluation Fund
Business Acquisition [Line Items]
Other Nonrecurring (Income) Expense			$ 2.5
Rhode Island Energy | Electric Customer
Business Acquisition [Line Items]
Public Utilities, Customer Bill Credit Agreement, Total	33.0
Rhode Island Energy | Natural Gas Customer
Business Acquisition [Line Items]
Public Utilities, Customer Bill Credit Agreement, Total	$ 17.0
Forecast [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs								$ 408.0