SHORT-TERM AND LONG-TERM DEBT	9 Months Ended
Sep. 30, 2017
Debt Disclosure [Abstract]
SHORT-TERM AND LONG-TERM DEBT	SHORT-TERM AND LONG-TERM DEBT Commercial Paper Programs and Credit Agreements: Eversource parent has a $1.45 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. As of September 30, 2017 and December 31, 2016, Eversource parent had $917.0 million and approximately $1.0 billion, respectively, in short-term borrowings outstanding under the Eversource parent commercial paper program, leaving $533.0 million and $428.0 million of available borrowing capacity as of September 30, 2017 and December 31, 2016, respectively. The weighted-average interest rate on these borrowings as of September 30, 2017 and December 31, 2016 was 1.34 percent and 0.88 percent, respectively. As of September 30, 2017, there were intercompany loans from Eversource parent of $202.3 million to PSNH and $96.9 million to WMECO. As of December 31, 2016, there were intercompany loans from Eversource parent of $80.1 million to CL&P, $160.9 million to PSNH and $51.0 million to WMECO. Eversource parent, CL&P, PSNH, WMECO, NSTAR Gas and Yankee Gas are parties to a five-year $1.45 billion revolving credit facility. The revolving credit facility terminates on September 4, 2021. The revolving credit facility serves to backstop Eversource parent's $1.45 billion commercial paper program. There were no borrowings outstanding on the revolving credit facility as of September 30, 2017 and December 31, 2016. Except as described below, amounts outstanding under the commercial paper programs are included in Notes Payable for Eversource and NSTAR Electric and are classified in current liabilities on the balance sheets as all borrowings are outstanding for no more than 364 days at one time. Intercompany loans from Eversource parent to CL&P, PSNH and WMECO are included in Notes Payable to Eversource Parent and are classified in current liabilities on their respective balance sheets. Intercompany loans from Eversource parent to CL&P, PSNH and WMECO are eliminated in consolidation on Eversource's balance sheets. As a result of the October 2017 Eversource parent long-term debt issuances, the net proceeds of which were used to repay short-term borrowings outstanding under the Eversource parent commercial paper program, $898.8 million of short-term debt was reclassified to Long-Term Debt as of September 30, 2017. NSTAR Electric has a $450 million commercial paper program allowing NSTAR Electric to issue commercial paper as a form of short-term debt. As of September 30, 2017, NSTAR Electric had no short-term borrowings outstanding and as of December 31, 2016, NSTAR Electric had $126.5 million in short-term borrowings outstanding under its commercial paper program, leaving $450.0 million and $323.5 million of available borrowing capacity as of September 30, 2017 and December 31, 2016, respectively. The weighted-average interest rate on these borrowings as of December 31, 2016 was 0.71 percent. NSTAR Electric is a party to a five-year $450 million revolving credit facility. The revolving credit facility terminates on September 4, 2021. The revolving credit facility serves to backstop NSTAR Electric's $450 million commercial paper program. There were no borrowings outstanding on the revolving credit facility as of September 30, 2017 and December 31, 2016. Long-Term Debt Issuances: In March 2017, Eversource parent issued $300 million of 2.75 percent Series K Senior Notes due to mature in 2022. The proceeds, net of issuance costs, were used to repay short-term borrowings under the Eversource parent commercial paper program. In March 2017, CL&P issued $300 million of 3.20 percent 2017 Series A First and Refunding Mortgage Bonds due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings. In May 2017, NSTAR Electric issued $350 million of 3.20 percent Debentures due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings and fund capital expenditures and working capital. In August 2017, CL&P issued $225 million of 4.30 percent 2014 Series A First and Refunding Mortgage Bonds due to mature in 2044. These bonds are part of the same series of CL&P’s existing 4.30 percent bonds that were initially issued in 2014. The aggregate outstanding principal amount for these bonds is now $475 million. The proceeds, net of issuance costs, were used to refinance short-term debt and fund capital expenditures and working capital. In September 2017, Yankee Gas issued $75 million of 3.02 percent Series N First Mortgage Bonds due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings. In October 2017, Eversource parent issued $450 million 2.75 percent Series K Senior Notes due to mature in 2022. These senior notes are part of the same series of Eversource parent’s existing 2.75 percent Series K Senior Notes that were initially issued in March 2017. The aggregate outstanding principal amount for the Series K Senior Notes is now $750 million. In addition, Eversource parent issued $450 million of 2.90 percent 2017 Series L Senior Notes due to mature in 2024. The proceeds, net of issuance costs, were used to repay short-term borrowings. In October 2017, NSTAR Electric issued $350 million of 3.20 percent Debentures due to mature in 2027. The debentures are part of the same series of NSTAR Electric’s existing 3.20 percent Debentures that were initially issued in May 2017. The aggregate outstanding principal amount for the 3.20 percent Debentures is now $700 million. The proceeds, net of issuance costs, will be used to redeem long-term debt due to mature on November 15, 2017. As the debt issuance refinanced short-term debt, the amount was reclassified to Long-Term Debt on Eversource's and NSTAR Electric's balance sheets. Long-Term Debt Repayments: In March 2017, CL&P repaid at maturity the $150 million 5.375 percent 2007 Series A First and Refunding Mortgage Bonds. In September 2017, CL&P repaid at maturity $100 million of 5.75 percent 2007 Series C First Mortgage Bonds and PSNH repaid at maturity $70 million of 6.15 percent 2007 Series N First Mortgage Bonds. In October 2017, NSTAR Gas repaid at maturity $25 million of 7.04 percent Series M First Mortgage Bonds. Long-Term Debt Issuance Authorizations: On January 4, 2017, PURA approved CL&P's request for authorization to issue up to $1.325 billion in long-term debt through December 31, 2020. On March 30, 2017, the DPU approved NSTAR Electric's request for authorization to issue up to $700 million in long-term debt through December 31, 2018.

SHORT-TERM AND LONG-TERM DEBT

Commercial Paper Programs and Credit Agreements: Eversource parent has a $1.45 billion commercial paper program allowing Eversource parent to issue commercial paper as a form of short-term debt. As of September 30, 2017 and December 31, 2016, Eversource parent had $917.0 million and approximately $1.0 billion, respectively, in short-term borrowings outstanding under the Eversource parent commercial paper program, leaving $533.0 million and $428.0 million of available borrowing capacity as of September 30, 2017 and December 31, 2016, respectively. The weighted-average interest rate on these borrowings as of September 30, 2017 and December 31, 2016 was 1.34 percent and 0.88 percent, respectively. As of September 30, 2017, there were intercompany loans from Eversource parent of $202.3 million to PSNH and $96.9 million to WMECO. As of December 31, 2016, there were intercompany loans from Eversource parent of $80.1 million to CL&P, $160.9 million to PSNH and $51.0 million to WMECO. Eversource parent, CL&P, PSNH, WMECO, NSTAR Gas and Yankee Gas are parties to a five-year $1.45 billion revolving credit facility. The revolving credit facility terminates on September 4, 2021. The revolving credit facility serves to backstop Eversource parent's $1.45 billion commercial paper program. There were no borrowings outstanding on the revolving credit facility as of September 30, 2017 and December 31, 2016.

Except as described below, amounts outstanding under the commercial paper programs are included in Notes Payable for Eversource and NSTAR Electric and are classified in current liabilities on the balance sheets as all borrowings are outstanding for no more than 364 days at one time. Intercompany loans from Eversource parent to CL&P, PSNH and WMECO are included in Notes Payable to Eversource Parent and are classified in current liabilities on their respective balance sheets. Intercompany loans from Eversource parent to CL&P, PSNH and WMECO are eliminated in consolidation on Eversource's balance sheets.

As a result of the October 2017 Eversource parent long-term debt issuances, the net proceeds of which were used to repay short-term borrowings outstanding under the Eversource parent commercial paper program, $898.8 million of short-term debt was reclassified to Long-Term Debt as of September 30, 2017.

NSTAR Electric has a $450 million commercial paper program allowing NSTAR Electric to issue commercial paper as a form of short-term debt. As of September 30, 2017, NSTAR Electric had no short-term borrowings outstanding and as of December 31, 2016, NSTAR Electric had $126.5 million in short-term borrowings outstanding under its commercial paper program, leaving $450.0 million and $323.5 million of available borrowing capacity as of September 30, 2017 and December 31, 2016, respectively. The weighted-average interest rate on these borrowings as of December 31, 2016 was 0.71 percent. NSTAR Electric is a party to a five-year $450 million revolving credit facility. The revolving credit facility terminates on September 4, 2021. The revolving credit facility serves to backstop NSTAR Electric's $450 million commercial paper program. There were no borrowings outstanding on the revolving credit facility as of September 30, 2017 and December 31, 2016.

Long-Term Debt Issuances: In March 2017, Eversource parent issued $300 million of 2.75 percent Series K Senior Notes due to mature in 2022. The proceeds, net of issuance costs, were used to repay short-term borrowings under the Eversource parent commercial paper program.

In March 2017, CL&P issued $300 million of 3.20 percent 2017 Series A First and Refunding Mortgage Bonds due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings.

In May 2017, NSTAR Electric issued $350 million of 3.20 percent Debentures due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings and fund capital expenditures and working capital.

In August 2017, CL&P issued $225 million of 4.30 percent 2014 Series A First and Refunding Mortgage Bonds due to mature in 2044. These bonds are part of the same series of CL&P’s existing 4.30 percent bonds that were initially issued in 2014. The aggregate outstanding principal amount for these bonds is now $475 million. The proceeds, net of issuance costs, were used to refinance short-term debt and fund capital expenditures and working capital.

In September 2017, Yankee Gas issued $75 million of 3.02 percent Series N First Mortgage Bonds due to mature in 2027. The proceeds, net of issuance costs, were used to repay short-term borrowings.

In October 2017, Eversource parent issued $450 million 2.75 percent Series K Senior Notes due to mature in 2022. These senior notes are part of the same series of Eversource parent’s existing 2.75 percent Series K Senior Notes that were initially issued in March 2017. The aggregate outstanding principal amount for the Series K Senior Notes is now $750 million. In addition, Eversource parent issued $450 million of 2.90 percent 2017 Series L Senior Notes due to mature in 2024. The proceeds, net of issuance costs, were used to repay short-term borrowings.

In October 2017, NSTAR Electric issued $350 million of 3.20 percent Debentures due to mature in 2027. The debentures are part of the same series of NSTAR Electric’s existing 3.20 percent Debentures that were initially issued in May 2017. The aggregate outstanding principal amount for the 3.20 percent Debentures is now $700 million. The proceeds, net of issuance costs, will be used to redeem long-term debt due to mature on November 15, 2017. As the debt issuance refinanced short-term debt, the amount was reclassified to Long-Term Debt on Eversource's and NSTAR Electric's balance sheets.

Long-Term Debt Repayments: In March 2017, CL&P repaid at maturity the $150 million 5.375 percent 2007 Series A First and Refunding Mortgage Bonds.

In September 2017, CL&P repaid at maturity $100 million of 5.75 percent 2007 Series C First Mortgage Bonds and PSNH repaid at maturity $70 million of 6.15 percent 2007 Series N First Mortgage Bonds.

In October 2017, NSTAR Gas repaid at maturity $25 million of 7.04 percent Series M First Mortgage Bonds.

Long-Term Debt Issuance Authorizations: On January 4, 2017, PURA approved CL&P's request for authorization to issue up to $1.325 billion in long-term debt through December 31, 2020. On March 30, 2017, the DPU approved NSTAR Electric's request for authorization to issue up to $700 million in long-term debt through December 31, 2018.