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EMPLOYEE BENEFITS - Schedule of Pension Benefit Obligations (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Pension and SERP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | $ (6,729.7) | $ (7,045.3) |
Service Cost | (70.1) | (85.8) | $ (76.2)
Interest Cost | (154.5) | (130.0) | (177.8)
Actuarial Gain | 1,385.8 | 177.1 |
Benefits Paid | 302.5 | 309.5 |
Benefits Paid - Lump Sum | 33.0 | 34.7 |
Benefits Paid - SERP | 12.9 | 10.1 |
Employee Transfers | 0.0 | 0.0 |
Benefit Obligation as of End of Year | (5,220.1) | (6,729.7) | (7,045.3)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 6,495.5 | 5,409.2 |
Actual Return on Plan Assets | (433.6) | 1,250.5 |
Employer Contributions | 80.0 | 180.0 |
Benefits Paid - Pension | (302.5) | (309.5) |
Benefits Paid - Lump Sum | (33.0) | (34.7) |
Employee Transfers | 0.0 | 0.0 |
Fair Value of Plan Assets as of End of Year | 5,806.4 | 6,495.5 | 5,409.2
Funded Status as of December 31st | 586.3 | (234.2) |
PBOP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (884.3) | (993.9) |
Service Cost | (11.6) | (13.5) | (10.2)
Interest Cost | (20.2) | (17.4) | (24.6)
Actuarial Gain | 173.6 | 81.4 |
Benefits Paid | 52.1 | 51.7 |
Employee Transfers | 0.0 | 0.0 |
Impact of Acquisitions | (3.3) | 7.4 |
Benefit Obligation as of End of Year | (693.7) | (884.3) | (993.9)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 1,138.3 | 1,004.1 |
Actual Return on Plan Assets | (119.6) | 183.2 |
Employer Contributions | 3.1 | 2.3 |
Benefits Paid - Pension | (51.7) | (51.3) |
Employee Transfers | 0.0 | 0.0 |
Fair Value of Plan Assets as of End of Year | 970.1 | 1,138.3 | 1,004.1
Funded Status as of December 31st | 276.4 | 254.0 |
CL&P | Pension and SERP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (1,330.9) | (1,477.3) |
Service Cost | (18.7) | (23.0) | (21.8)
Interest Cost | (31.3) | (27.3) | (37.3)
Actuarial Gain | 284.1 | 127.8 |
Benefits Paid | 63.3 | 64.6 |
Benefits Paid - Lump Sum | 0.0 | 0.0 |
Benefits Paid - SERP | 0.3 | 0.3 |
Employee Transfers | 3.2 | 4.0 |
Benefit Obligation as of End of Year | (1,030.0) | (1,330.9) | (1,477.3)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 1,323.8 | 1,043.1 |
Actual Return on Plan Assets | (85.3) | 250.4 |
Employer Contributions | 0.0 | 98.9 |
Benefits Paid - Pension | (63.3) | (64.6) |
Benefits Paid - Lump Sum | 0.0 | 0.0 |
Employee Transfers | (3.2) | (4.0) |
Fair Value of Plan Assets as of End of Year | 1,172.0 | 1,323.8 | 1,043.1
Funded Status as of December 31st | 142.0 | (7.1) |
CL&P | PBOP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (165.5) | (178.6) |
Service Cost | (2.0) | (2.3) | (1.7)
Interest Cost | (3.7) | (3.2) | (4.4)
Actuarial Gain | 33.0 | 5.8 |
Benefits Paid | 10.4 | 10.9 |
Employee Transfers | (0.1) | 1.9 |
Impact of Acquisitions | 0.0 | 0.0 |
Benefit Obligation as of End of Year | (127.9) | (165.5) | (178.6)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 145.7 | 134.1 |
Actual Return on Plan Assets | (15.0) | 24.1 |
Employer Contributions | 0.0 | 0.0 |
Benefits Paid - Pension | (10.4) | (10.9) |
Employee Transfers | 0.3 | (1.6) |
Fair Value of Plan Assets as of End of Year | 120.6 | 145.7 | 134.1
Funded Status as of December 31st | (7.3) | (19.8) |
NSTAR Electric | Pension and SERP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (1,448.4) | (1,517.9) |
Service Cost | (13.8) | (15.8) | (15.4)
Interest Cost | (32.8) | (26.8) | (38.6)
Actuarial Gain | 295.5 | 20.8 |
Benefits Paid | 68.4 | 68.7 |
Benefits Paid - Lump Sum | 14.8 | 15.6 |
Benefits Paid - SERP | 0.2 | 0.2 |
Employee Transfers | 5.7 | 6.8 |
Benefit Obligation as of End of Year | (1,110.4) | (1,448.4) | (1,517.9)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 1,596.0 | 1,345.1 |
Actual Return on Plan Assets | (103.3) | 312.0 |
Employer Contributions | 15.0 | 30.0 |
Benefits Paid - Pension | (68.4) | (68.7) |
Benefits Paid - Lump Sum | (14.8) | (15.6) |
Employee Transfers | (5.7) | (6.8) |
Fair Value of Plan Assets as of End of Year | 1,418.8 | 1,596.0 | 1,345.1
Funded Status as of December 31st | 308.4 | 147.6 |
NSTAR Electric | PBOP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (238.4) | (260.5) |
Service Cost | (2.0) | (2.4) | (2.1)
Interest Cost | (5.3) | (4.4) | (6.6)
Actuarial Gain | 39.4 | 11.5 |
Benefits Paid | 16.6 | 16.3 |
Employee Transfers | 0.2 | 1.1 |
Impact of Acquisitions | 0.0 | 0.0 |
Benefit Obligation as of End of Year | (189.5) | (238.4) | (260.5)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 530.0 | 464.6 |
Actual Return on Plan Assets | (57.0) | 84.2 |
Employer Contributions | 0.0 | 0.0 |
Benefits Paid - Pension | (16.6) | (16.3) |
Employee Transfers | (0.3) | (2.5) |
Fair Value of Plan Assets as of End of Year | 456.1 | 530.0 | 464.6
Funded Status as of December 31st | 266.6 | 291.6 |
PSNH | Pension and SERP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (721.0) | (748.7) |
Service Cost | (6.9) | (8.9) | (8.2)
Interest Cost | (16.9) | (14.5) | (19.4)
Actuarial Gain | 156.7 | 14.7 |
Benefits Paid | 33.9 | 34.7 |
Benefits Paid - Lump Sum | 1.0 | 0.0 |
Benefits Paid - SERP | 0.4 | 0.4 |
Employee Transfers | (3.4) | 1.3 |
Benefit Obligation as of End of Year | (556.2) | (721.0) | (748.7)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 694.6 | 593.7 |
Actual Return on Plan Assets | (45.1) | 136.9 |
Employer Contributions | 0.0 | 0.0 |
Benefits Paid - Pension | (33.9) | (34.7) |
Benefits Paid - Lump Sum | (1.0) | 0.0 |
Employee Transfers | 3.4 | (1.3) |
Fair Value of Plan Assets as of End of Year | 618.0 | 694.6 | 593.7
Funded Status as of December 31st | 61.8 | (26.4) |
PSNH | PBOP |  |  |
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] |  |  |
Benefit Obligation as of Beginning of Year | (92.3) | (109.5) |
Service Cost | (1.1) | (1.2) | (0.9)
Interest Cost | (2.2) | (1.8) | (2.8)
Actuarial Gain | 15.2 | 14.6 |
Benefits Paid | 6.0 | 5.6 |
Employee Transfers | (0.2) | 0.0 |
Impact of Acquisitions | 0.0 | 0.0 |
Benefit Obligation as of End of Year | (74.6) | (92.3) | (109.5)
Change in Pension Plan Assets: |  |  |
Fair Value of Plan Assets as of Beginning of Year | 88.0 | 79.4 |
Actual Return on Plan Assets | (9.8) | 14.2 |
Employer Contributions | 0.0 | 0.0 |
Benefits Paid - Pension | (6.0) | (5.6) |
Employee Transfers | 0.1 | 0.0 |
Fair Value of Plan Assets as of End of Year | 72.3 | 88.0 | $ 79.4
Funded Status as of December 31st | $ (2.3) | $ (4.3) |

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