Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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No definition available.

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 944
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-Section S99
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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SHORT-TERM AND LONG-TERM DEBT - Summary of Long-Term Debt Issuance and Repayments (Details) - USD ($) $ in Thousands	1 Months Ended						9 Months Ended
	Sep. 30, 2020	Aug. 31, 2020	May 31, 2020	Apr. 30, 2020	Mar. 31, 2020	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Repayments							$ (302,236)	$ (250,855)
Senior Notes \| Eversource Parent 3.45% Series P Senior Notes \| Eversource Parent
Debt Instrument [Line Items]
Issuances		$ 300,000				$ 350,000
Interest rate, stated percentage		3.45%				3.45%
Aggregate outstanding principal amount	$ 650,000						650,000
Senior Notes \| Eversource Parent 0.80% Series Q Senior Notes \| Eversource Parent
Debt Instrument [Line Items]
Issuances		$ 300,000
Interest rate, stated percentage		0.80%
Senior Notes \| Eversource Parent 1.65% Series R Senior Notes \| Eversource Parent
Debt Instrument [Line Items]
Issuances		$ 600,000
Interest rate, stated percentage		1.65%
NSTAR Electric
Debt Instrument [Line Items]
Repayments							$ (95,000)	$ 0
NSTAR Electric \| Senior Notes \| 3.95% 2020 Debentures
Debt Instrument [Line Items]
Issuances					$ 400,000
Interest rate, stated percentage					3.95%
NSTAR Electric \| Senior Notes \| 5.10% Series E Senior Notes
Debt Instrument [Line Items]
Repayments					$ (95,000)
Interest rate, stated percentage					5.10%
PSNH \| Senior Notes \| 2.40% Series U First Mortgage Bonds
Debt Instrument [Line Items]
Issuances		$ 150,000
Interest rate, stated percentage		2.40%
NSTAR Gas \| Senior Notes \| NSTAR Gas 4.46% Series N First Mortgage Bonds
Debt Instrument [Line Items]
Repayments						$ (125,000)
Interest rate, stated percentage						4.46%
NSTAR Gas \| Senior Notes \| NSTAR Gas 2.33% Series R First Mortgage Bonds
Debt Instrument [Line Items]
Issuances			$ 75,000
Interest rate, stated percentage			2.33%
NSTAR Gas \| Senior Notes \| NSTAR Gas 3.15% Series S First Mortgage Bonds
Debt Instrument [Line Items]
Issuances			$ 115,000
Interest rate, stated percentage			3.15%
Yankee Gas \| Senior Notes \| Yankee Gas 4.87% Series K First Mortgage Bonds
Debt Instrument [Line Items]
Repayments				$ (50,000)
Interest rate, stated percentage				4.87%
Yankee Gas \| Senior Notes \| Yankee Gas 2.90% Series R First Mortgage Bonds
Debt Instrument [Line Items]
Issuances	$ 70,000
Interest rate, stated percentage	2.90%						2.90%
Aquarion \| Term Loans and Mortgage Bonds \| Aquarion Water Company of Massachusetts, Inc. and Aquarion Water Capital of Massachusetts, Inc. various term loans and general mortgage bonds
Debt Instrument [Line Items]
Repayments	$ (32,200)