CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Activities:
Net Income	$ 1,412,394	$ 1,228,046	$ 1,212,686
Adjustments to Reconcile Net Income to Net Cash Flows Provided by Operating Activities:
Depreciation	1,194,246	1,103,008	981,380
Deferred Income Taxes	346,779	347,056	257,154
Uncollectible Expense	61,876	60,886	53,461
Pension, SERP and PBOP (Income)/Expense, Net	(160,857)	(14,693)	12,888
Pension and PBOP Contributions	(83,148)	(182,344)	(111,524)
Regulatory Under Recoveries, Net	(205,294)	(314,211)	(516,411)
(Customer Credits)/Reserve at CL&P related to PURA Settlement Agreement and Storm Performance Penalty	(72,041)	81,274	0
Amortization	448,892	231,965	177,679
Cost of Removal Expenditures	(303,755)	(242,130)	(148,332)
Payment of Withheld Property Taxes	(78,446)	0	0
Other	(39,192)	(64,640)	(25,957)
Changes in Current Assets and Liabilities:
Receivables and Unbilled Revenues, Net	(470,593)	(135,505)	(351,843)
Taxes Receivable/Accrued, Net	18,358	(110,621)	43,819
Accounts Payable	377,657	(29,201)	122,567
Other Current Assets and Liabilities, Net	(45,583)	3,710	(24,995)
Net Cash Flows Provided by Operating Activities	2,401,293	1,962,600	1,682,572
Investing Activities:
Investments in Property, Plant and Equipment	(3,441,852)	(3,175,080)	(2,942,996)
Proceeds from Sales of Marketable Securities	457,612	447,893	434,124
Purchases of Marketable Securities	(424,174)	(414,980)	(401,823)
Acquisition of Assets of Columbia Gas of Massachusetts, Net of Restricted Cash	0	0	(1,113,252)
Investments in Unconsolidated Affiliates	(742,496)	(327,385)	(239,673)
Other Investing Activities	20,420	22,178	23,809
Net Cash Flows Used in Investing Activities	(4,130,490)	(3,447,374)	(4,129,275)
Financing Activities:
Issuance of Common Shares, Net of Issuance Costs	197,058	0	928,992
Cash Dividends on Common Shares	(860,033)	(805,439)	(744,665)
Cash Dividends on Preferred Stock	(7,519)	(7,519)	(7,519)
(Decrease)/Increase in Notes Payable	(78,170)	256,125	13,955
Repayment of Rate Reduction Bonds	(43,210)	(43,210)	(43,210)
Issuance of Long-Term Debt	4,045,000	3,230,000	2,760,000
Retirement of Long-Term Debt	(1,175,000)	(1,142,500)	(327,236)
Other Financing Activities	(48,185)	(46,625)	14,273
Net Cash Flows Provided by Financing Activities	2,029,941	1,440,832	2,594,590
Net Increase/(Decrease) in Cash, Cash Equivalents and Restricted Cash	300,744	(43,942)	147,887
Cash, Cash Equivalents and Restricted Cash - Beginning of Year	221,008	264,950	117,063
Cash, Cash Equivalents and Restricted Cash - End of Year	521,752	221,008	264,950
Hingham Water System
Investing Activities:
Proceeds from the Sale of Hingham Water System	$ 0	$ 0	$ 110,536