LONG-TERM DEBT (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Maturities of Long-term Debt

Details of long-term debt outstanding are as follows:

CL&P (Millions of Dollars)	As of December 31,
	2017			2016
First Mortgage Bonds:
7.875% 1994 Series D due 2024	$	139.8		$	139.8
5.750% 2004 Series B due 2034	130.0			130.0
5.625% 2005 Series B due 2035	100.0			100.0
6.350% 2006 Series A due 2036	250.0			250.0
5.375% 2007 Series A due 2017	—			150.0
5.750% 2007 Series B due 2037	150.0			150.0
5.750% 2007 Series C due 2017	—			100.0
6.375% 2007 Series D due 2037	100.0			100.0
5.650% 2008 Series A due 2018	300.0			300.0
5.500% 2009 Series A due 2019	250.0			250.0
2.500% 2013 Series A due 2023	400.0			400.0
4.300% 2014 Series A due 2044	475.0			250.0
4.150% 2015 Series A due 2045	350.0			350.0
3.200% 2017 Series A due 2027	300.0			—
Total First Mortgage Bonds	2,944.8			2,669.8
Pollution Control Revenue Bonds:
4.375% Fixed Rate Tax Exempt due 2028	120.5			120.5
Less Amounts due Within One Year	(300.0		)	(250.0		)
Unamortized Premiums and Discounts, Net	11.5			(10.0		)
Unamortized Debt Issuance Costs	(17.7		)	(14.3		)
CL&P Long-Term Debt	$	2,759.1		$	2,516.0

NSTAR Electric (Millions of Dollars)	As of December 31,
	2017			2016
Debentures:
5.750% due 2036	$	200.0		$	200.0
5.625% due 2017	—			400.0
5.500% due 2040	300.0			300.0
2.375% due 2022	400.0			400.0
4.400% due 2044	300.0			300.0
3.250% due 2025	250.0			250.0
2.700% due 2026	250.0			250.0
3.200% due 2027	700.0			—
Total Debentures	2,400.0			2,100.0
Notes:
5.900% Senior Notes Series B due 2034	50.0			50.0
6.700% Senior Notes Series D due 2037	40.0			40.0
5.100% Senior Notes Series E due 2020	95.0			95.0
3.500% Senior Notes Series F due 2021	250.0			250.0
3.880% Senior Notes Series G due 2023	80.0			80.0
2.750% Senior Notes Series H due 2026	50.0			50.0
Total Notes	565.0			565.0
Less Amounts due Within One Year	—			(400.0		)
Unamortized Premiums and Discounts, Net	(1.8		)	(4.9		)
Unamortized Debt Issuance Costs	(19.4		)	(15.5		)
NSTAR Electric Long-Term Debt	$	2,943.8		$	2,244.6

PSNH (Millions of Dollars)	As of December 31,
	2017			2016
First Mortgage Bonds:
5.600% Series M due 2035	$	50.0		$	50.0
6.150% Series N due 2017	—			70.0
6.000% Series O due 2018	110.0			110.0
4.500% Series P due 2019	150.0			150.0
4.050% Series Q due 2021	122.0			122.0
3.200% Series R due 2021	160.0			160.0
3.500% Series S due 2023	325.0			325.0
Total First Mortgage Bonds	917.0			987.0
Pollution Control Revenue Bonds:
Adjustable Rate Tax Exempt Series A due 2021      (2.048% and 1.138% as of December 31, 2017 and 2016, respectively)	89.3			89.3
Less Amounts due Within One Year	(110.0		)	(70.0		)
Unamortized Premiums and Discounts, Net	0.2			0.1
Unamortized Debt Issuance Costs	(4.1		)	(4.4		)
PSNH Long-Term Debt	$	892.4		$	1,002.0

OTHER (Millions of Dollars)	As of December 31,
	2017			2016
Yankee Gas - First Mortgage Bonds: 3.020% - 8.480% due 2018 - 2044	$	520.0		$	445.0
NSTAR Gas - First Mortgage Bonds: 4.350% - 9.950% due 2020 - 2045	285.0			310.0
Eversource Parent and Other - Notes and Debentures:
4.500% Debentures due 2019	350.0			350.0
1.450% - 4.000% Senior Notes due 2018 - 2026	3,260.0			1,700.0
Notes Payable Unsecured 3.57% - 6.430% due 2021 - 2037	290.9			—
Notes Payable Secured 4.10% - 9.64% due 2021 - 2035	70.4			—
Pre-1983 Spent Nuclear Fuel Obligation (CYAPC)	181.4			180.0
Fair Value Adjustment (1)	172.6			144.6
Less Fair Value Adjustment - Current Portion (1)	(35.4		)	(28.9		)
Less Amounts due in One Year	(104.2		)	(25.0		)
Commercial Paper Classified as Long-Term Debt	201.2			—
Unamortized Premiums and Discounts, Net	1.5			(1.8		)
Unamortized Debt Issuance Costs	(12.8		)	(7.1		)
Total Other Long-Term Debt	5,180.6			$	3,066.8
Total Eversource Long-Term Debt	11,775.9			$	8,829.4

(1) The fair value adjustment amount is the purchase price adjustments, net of amortization, required to record the NSTAR long-term debt at fair value on the date of the 2012 merger and to record the Aquarion long-term debt at fair value as of December 4, 2017.

Schedule of Long-term Debt Instruments

Long-term debt maturities on debt outstanding for the years 2018 through 2022 and thereafter are shown below. These amounts exclude the CYAPC pre-1983 spent nuclear fuel obligation, net unamortized premiums, discounts and debt issuance costs, and other fair value adjustments as of December 31, 2017:

(Millions of Dollars)	Eversource		CL&P		NSTAR Electric		PSNH
2018	$	961.0	$	300.0	$	—	$	110.0
2019	801.0		250.0		—		150.0
2020	296.1		—		95.0		—
2021	922.8		—		250.0		371.3
2022	1,188.9		—		400.0		—
Thereafter	7,643.1		2,515.3		2,220.0		375.0
Total	$	11,812.9	$	3,065.3	$	2,965.0	$	1,006.3

The following table summarizes long-term debt issuances and repayments:

(Millions of Dollars)	Issue Date	Issuances/(Repayments)			Maturity Date	Use of Proceeds
CL&P:
3.20% 2017 Series A First Mortgage Bonds	March 2017	$	300.0		2027	Repay short-term debt borrowings
4.30% 2014 Series A First Mortgage Bonds (1)	August 2017	225.0			2044	Refinance short-term debt and fund working capital and capital expenditures
5.375% 2007 Series A First Mortgage Bonds	March 2007	(150.0		)	2017	N/A
5.75% 2007 Series C First Mortgage Bonds	September 2007	(100.0		)	2017	N/A
NSTAR Electric:
3.20% Debentures	May 2017	350.0			2027	Repay short-term borrowings and fund capital expenditures and working capital
3.20% Debentures (2)	October 2017	350.0			2027	Redeem long-term debt that matured in 2017
5.625% Debentures	November 2007	(400.0		)	2017	N/A
PSNH:
6.15% Series N First Mortgage Bonds	September 2007	(70.0		)	2017	N/A
Other:
Yankee Gas 3.02% Series N First Mortgage Bonds	September 2017	75.0			2027	Repay short-term borrowings
NSTAR Gas 7.04% Series M First Mortgage Bonds	September 1997	(25.0		)	2017	N/A
Eversource Parent 2.75% Series K Senior Notes	March 2017	300.0			2022	Repay short-term borrowings
Eversource Parent 2.75% Series K Senior Notes (3)	October 2017	450.0			2022	Repay short-term borrowings
Eversource Parent 2.90% Series L Senior Notes	October 2017	450.0			2024	Repay short-term borrowings
Eversource Parent 2.50% Series I Senior Notes (4)	January 2018	200.0			2021	Repay long-term debt due to mature in 2018 and repay short-term borrowings
Eversource Parent 3.30% Series M Senior Notes	January 2018	450.0			2028	Repay long-term debt due to mature in 2018
Eversource Parent 1.60% Series G Senior Notes (5)	January 2015	(150.0		)	2018	N/A

(1) These bonds are part of the existing series initially issued by CL&P in 2014. The aggregate outstanding principal amount for these bonds is now $475 million.

(2) These debentures are part of the same series initially issued by NSTAR Electric in May 2017. The aggregate outstanding principal amount for these debentures is now $700 million.

(3) These notes are part of the same series issued by Eversource parent in March 2017. The aggregate outstanding principal amount for these notes is now $750 million.

(4) These notes are part of the same series issued by Eversource parent in March 2016. The aggregate outstanding principal amount for these notes is now $450 million.

(5) Represents a repayment at maturity on January, 15 2018.