Acquisitions, Development and Divestitures - Acquisitions (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended		7 Months Ended	12 Months Ended
	May 25, 2022	Jun. 30, 2022	Jun. 30, 2022	Sep. 30, 2022	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disclosure [Line Items]
Goodwill, Acquired During Period, After Remeasurement									$ 1,585.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-Term Debt		$ 1,500.0	$ 1,500.0		$ 1,500.0
Operating Revenues								$ 8,312.0	7,902.0	$ 5,783.0
Net income (loss)								740.0	756.0	(1,480.0)
Business Acquisition, Pro Forma Revenue								8,667.0	7,478.0
Business Acquisition, Pro Forma Net Income (Loss)								790.0	159.0
Business Combination, Integration Related Costs									223.0	38.0
Transition Service Agreement Expense								228.0	123.0
Goodwill							$ 2,248.0	2,247.0	2,248.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables, Gross	$ 255.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, AR Reserve	60.0
Business Combination, Transaction Costs Expense									18.0
Payments to Acquire Businesses, Gross					5,300.0
Disposal Group [Line Items]
Income (Loss) from Discontinued Operations (net of income taxes)								0.0	42.0	(1,498.0)
Payments to Acquire Businesses, Gross					5,300.0
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
Business Combination, Integration Related Costs									223.0	38.0
Corporate And Other [Member]
Disclosure [Line Items]
Goodwill, Acquired During Period, After Remeasurement									860.0
Operating Revenues								1.0	23.0	33.0
Net income (loss)								(427.0)	(316.0)	(935.0)
Goodwill, Purchase Accounting Adjustments								1.0
Goodwill							861.0	860.0	861.0	53.0
Rhode Island Regulated
Disclosure [Line Items]
Operating Revenues								1,851.0	1,038.0	0.0
Net income (loss)								96.0	(44.0)	0.0
Goodwill							725.0	725.0	725.0	0.0
Rhode Island Energy
Disclosure [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	154.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables	195.0
Business Acquisition, Recognized Identifiable Assets Acquired and Liabilities Assumed, Unbilled Revenues	54.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Regulatory Assets	75.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	65.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	642.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	3,992.0
Public Utilities, Customer Bill Credit Agreement, Total	50.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Regulatory Assets	393.0
Goodwill, Business Combination	1,585.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	164.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets	6,134.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	6,776.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-Term Debt	14.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable	180.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Taxes Accrued	44.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Other	198.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	675.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-Term Debt	1,496.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Regulatory Liabilities	643.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	142.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities	2,281.0
Business Combination, Consideration Transferred		$ 3,820.0
Operating Revenues							1,038.0
Net income (loss)							(44.0)
Acquisition commitment write off expenses									98.0
RICCREF Contribution Expense			2.5
Accounts Receivable Forgiven, AR Reserve									23.0
Accounts Receivable Forgiven, net				$ 21.0
Accounts Receivable Forgiven, Gross				44.0
Public Utilities, Customer Bill Credit Agreement, Net of Tax	40.0
Business Combination, Regulatory Assets Expensed					20.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Regulatory Liabilities	239.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Price Risk Management Assets	99.0
Disposal Group [Line Items]
Accounts Receivable Forgiven, AR Reserve									23.0
Rhode Island Energy | Electric Customer
Disclosure [Line Items]
Public Utilities, Customer Bill Credit Agreement, Total	33.0
Rhode Island Energy | Natural Gas Customer
Disclosure [Line Items]
Public Utilities, Customer Bill Credit Agreement, Total	$ 17.0
Rhode Island Energy | Accounts Receivable and Regulatory Asset write off
Disclosure [Line Items]
Acquisition commitment write off expenses									43.0
Rhode Island Energy | Accrued expenditures for the RIAG and decarbonization goals
Disclosure [Line Items]
Acquisition commitment write off expenses									5.0
Rhode Island Energy | RIPUC regulatory liability
Disclosure [Line Items]
Regulatory Liabilities				$ 50.0			$ 50.0		50.0
Rhode Island Energy | Rhode Island Energy TSA
Disclosure [Line Items]
Other Nonrecurring (Income) Expense								262.0	181.0
Rhode Island Energy | Accrual for TSA Markup
Disclosure [Line Items]
Other Nonrecurring (Income) Expense								7.0	3.0
Rhode Island Energy | Accrual for RIAG Evaluation Fund
Disclosure [Line Items]
Other Nonrecurring (Income) Expense			$ 2.5
WPD [Member]
Disposal Group [Line Items]
Income tax related to Discontinued Operations								0.0	(42.0)	759.0
Transaction Costs | Additional Costs Related to Purchase, Agreed not to seek recovery
Disclosure [Line Items]
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized								28.0
Transaction Costs | Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses | Additional Costs Related to Purchase, Agreed not to seek recovery
Disclosure [Line Items]
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized									18.0	10.0
Discontinued Operations, Disposed of by Sale | WPD [Member]
Disposal Group [Line Items]
Income (Loss) from Discontinued Operations (net of income taxes)										(1,498.0)
Disposal Group, Held-for-sale, Not Discontinued Operations | Safari Holdings LLC, Consolidated
Disposal Group [Line Items]
Gain (loss) on disposition of business, net of tax								5.0	46.0
Loss on Sale								$ 6.0	60.0
Discontinued Operations, Held-for-sale | WPD [Member]
Disposal Group [Line Items]
Sale proceeds, net of realized foreign currency hedge losses						$ 10,700.0
Net Proceeds From Divestiture Of Businesses						$ 10,400.0
Operating Revenues related to discontinued operations									0.0	1,344.0
Operating Expense related to discontinued operations									0.0	467.0
Other Income (Expense) - net related to discontinued operations									0.0	202.0
Interest Expense related to discontinued operations									0.0	209.0
Income from Discontinued Operations, before Income Tax									0.0	870.0
Loss on Sale									0.0	(1,609.0)
Income tax related to Discontinued Operations									(42.0)	759.0
Income (Loss) from Discontinued Operations (net of income taxes)									$ 42.0	$ (1,498.0)
Narragansett Electric
Disclosure [Line Items]
Business Combination, Consideration Transferred					$ 3,800.0