XML 42 R2.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Pay vs Performance Disclosure | 12 Months Ended
--- | ---
Dec. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($)
Pay vs Performance Disclosure |  |  |  |  |
Pay vs Performance Disclosure, Table |
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | Value of Initial Fixed $100 Investment Based on | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | Fiscal Year | ​ | ​ | SCT Total PEO #1(1) | ​ | ​ | CAP PEO #1(1) | ​ | ​ | SCT Total PEO #2(1) | ​ | ​ | CAP PEO #2(1) | ​ | ​ | Average SCT Non-PEO NEOs(2) | ​ | ​ | CAP Non-PEO NEOs(2) | ​ | ​ | Company TSR(3) | ​ | ​ | Peer Group TSR(3) | ​ | ​ | Net Income (GAAP) | ​ | ​ | Company Selected Measure (EPS Non-GAAP)(4) | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​ | ​ | j | ​ | ​ | k | ​
​ | 1 (2024) | ​ | ​ | ​ | ​ | 13,578,154 | ​ | ​ | ​ | ​ | ​ | 9,503,340 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | 3,496,586 | ​ | ​ | ​ | ​ | ​ | 2,647,958 | ​ | ​ | ​ | ​ | ​ | 80 | ​ | ​ | ​ | ​ | ​ | 127 | ​ | ​ | ​ | ​ | ​ | 811.7 | ​ | ​ | ​ | ​ | ​ | 4.57 | ​ | ​
​ | 2 (2023) | ​ | ​ | ​ | ​ | 18,885,577 | ​ | ​ | ​ | ​ | ​ | 7,429,247 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | 2,936,041 | ​ | ​ | ​ | ​ | ​ | 1,135,182 | ​ | ​ | ​ | ​ | ​ | 82 | ​ | ​ | ​ | ​ | ​ | 107 | ​ | ​ | ​ | ​ | ​ | -442.2 | ​ | ​ | ​ | ​ | ​ | 4.34 | ​ | ​
​ | 3 (2022) | ​ | ​ | ​ | ​ | 12,959,134 | ​ | ​ | ​ | ​ | ​ | 10,858,066 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | 3,410,910 | ​ | ​ | ​ | ​ | ​ | 2,951,647 | ​ | ​ | ​ | ​ | ​ | 107 | ​ | ​ | ​ | ​ | ​ | 117 | ​ | ​ | ​ | ​ | ​ | 1,404.9 | ​ | ​ | ​ | ​ | ​ | 4.09 | ​ | ​
​ | 4 (2021) | ​ | ​ | ​ | ​ | 6,467,078 | ​ | ​ | ​ | ​ | ​ | 5,120,192 | ​ | ​ | ​ | ​ | ​ | 10,220,941 | ​ | ​ | ​ | ​ | ​ | 10,910,465 | ​ | ​ | ​ | ​ | ​ | 4,157,260 | ​ | ​ | ​ | ​ | ​ | 3,471,045 | ​ | ​ | ​ | ​ | ​ | 113 | ​ | ​ | ​ | ​ | ​ | 116 | ​ | ​ | ​ | ​ | ​ | 1,220.5 | ​ | ​ | ​ | ​ | ​ | 3.86 | ​ | ​
​ | 5 (2020) | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | 14,575,276 | ​ | ​ | ​ | ​ | ​ | 14,062,876 | ​ | ​ | ​ | ​ | ​ | 5,002,344 | ​ | ​ | ​ | ​ | ​ | 3,960,432 | ​ | ​ | ​ | ​ | ​ | 105 | ​ | ​ | ​ | ​ | ​ | 99 | ​ | ​ | ​ | ​ | ​ | 1,205.2 | ​ | ​ | ​ | ​ | ​ | 3.64 | ​ | ​
(1) The PEOs for each year are as follows: ​ a. 2024, 2023, 2022 and 2021 — Joseph R. Nolan, Jr. ​ b. 2020 and 2021 — James J. Judge. Mr. Nolan became the Company’s Chief Executive Officer on May 5, 2021 ​ (2) The Non-PEO NEOs for each year are as follows: ​ a. 2024 — John Moreira, Paul Chodak, III, Susan Sgroi and Gregory B. Butler 2023 — John M. Moreira, Gregory B. Butler, Christine M. Carmody, James W. Hunt, III and Werner J. Schweiger ​ c. 2022 — John M. Moreira, Gregory B. Butler, Christine M. Carmody, Werner J. Schweiger, James J. Judge and Philip J. Lembo ​ d. 2021 — Philip J. Lembo, Werner J. Schweiger, Gregory B. Butler and Christine M. Carmody ​ e. 2020 — Philip J. Lembo, Werner J. Schweiger, Gregory B. Butler and Joseph R. Nolan, Jr. ​ (3) The values disclosed in this TSR column represent the measurement period value of an investment of $100 in our units as of December 31, 2020, and then valued again on each of December 31, 2021, December 31, 2022, December 31, 2023 and December 31, 2024 as compared to the EEI Index, as disclosed in our Annual Report on Form 10-K for fiscal year ended 2024 pursuant to Item 201(e) of Regulation S-K ​ (4) Set forth in Footnote 1 on page 39 and Exhibit A to the CD&A is a full description of how non-GAAP EPS was determined. The Company believes non-GAAP EPS is a very important measure to investors and which is indicative of Company performance; accordingly, it represents a significant factor in determining both annual and long term executive compensation, though as noted the Compensation Committee determined that due to the disappointing performance in our 2024 stock price, the Committee reduced payout for the EPS-based goal in our 2024 annual incentive plan to 75 percent from an indicative payout in the range of 125 to 200 percent. To calculate CAP for our PEOs and Non-PEO NEOs in the table above, the following amounts were deducted and added to the values as reported in the SCT:
​ | Fiscal Year | ​ | ​ | SCT Total PEO #1 | ​ | ​ | Pension Deducted from SCT | ​ | ​ | Pension Service Value Added to SCT | ​ | ​ | Stock Awards Deducted from SCT | ​ | ​ | Fair Value of Equity Awards Granted during the Year and Remained Unvested at Year-End | ​ | ​ | Change in Fair Value of Unvested Equity Awards that Vested During the Year | ​ | ​ | Change in Fair Value of Unvested Equity Grants | ​ | ​ | CAP PEO #1 | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​
​ | 1 (2024) | ​ | ​ | ​ | ​ | 13,578,154 | ​ | ​ | ​ | ​ | ​ | -2,188,733 | ​ | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​ | ​ | ​ | ​ | -7,510,128 | ​ | ​ | ​ | ​ | ​ | 7,266,337 | ​ | ​ | ​ | ​ | ​ | -308,543 | ​ | ​ | ​ | ​ | ​ | -2,778,136 | ​ | ​ | ​ | ​ | ​ | 9,503,340 | ​ | ​
​ | 2 (2023) | ​ | ​ | ​ | ​ | 18,885,577 | ​ | ​ | ​ | ​ | ​ | -7,832,472 | ​ | ​ | ​ | ​ | ​ | 689,828 | ​ | ​ | ​ | ​ | ​ | -8,018,396 | ​ | ​ | ​ | ​ | ​ | 6,023,948 | ​ | ​ | ​ | ​ | ​ | -182,331 | ​ | ​ | ​ | ​ | ​ | -2,136,906 | ​ | ​ | ​ | ​ | ​ | 7,429,247 | ​ | ​
​ | 3 (2022) | ​ | ​ | ​ | ​ | 12,959,134 | ​ | ​ | ​ | ​ | ​ | -2,143,443 | ​ | ​ | ​ | ​ | ​ | 429,463 | ​ | ​ | ​ | ​ | ​ | -6,825,923 | ​ | ​ | ​ | ​ | ​ | 6,749,195 | ​ | ​ | ​ | ​ | ​ | -235,802 | ​ | ​ | ​ | ​ | ​ | -74,557 | ​ | ​ | ​ | ​ | ​ | 10,858,066 | ​ | ​
​ | 4 (2021) | ​ | ​ | ​ | ​ | 6,467,078 | ​ | ​ | ​ | ​ | ​ | -1,705,782 | ​ | ​ | ​ | ​ | ​ | 336,850 | ​ | ​ | ​ | ​ | ​ | -1,441,650 | ​ | ​ | ​ | ​ | ​ | 1,546,319 | ​ | ​ | ​ | ​ | ​ | -201,335 | ​ | ​ | ​ | ​ | ​ | 118,712 | ​ | ​ | ​ | ​ | ​ | 5,120,192 | ​ | ​
​ | Fiscal Year | ​ | ​ | SCT Total PEO #2 | ​ | ​ | Pension Deducted from SCT | ​ | ​ | Pension Service Value Added to SCT | ​ | ​ | Stock Awards Deducted from SCT | ​ | ​ | Fair Value of Equity Awards Granted during the Year and Remained Unvested at Year-End | ​ | ​ | Change in Fair Value of Unvested Equity Awards that Vested During the Year | ​ | ​ | Change in Fair Value of Unvested Equity Grants | ​ | ​ | CAP PEO #2 | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​
​ | (2021) | ​ | ​ | ​ | ​ | 10,220,941 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 845,242 | ​ | ​ | ​ | ​ | ​ | -6,786,337 | ​ | ​ | ​ | ​ | ​ | 7,279,051 | ​ | ​ | ​ | ​ | ​ | -1,266,246 | ​ | ​ | ​ | ​ | ​ | 617,814 | ​ | ​ | ​ | ​ | ​ | 10,910,465 | ​ | ​
​ | (2020) | ​ | ​ | ​ | ​ | 14,575,276 | ​ | ​ | ​ | ​ | ​ | -3,742,215 | ​ | ​ | ​ | ​ | ​ | 111,326 | ​ | ​ | ​ | ​ | ​ | -6,682,612 | ​ | ​ | ​ | ​ | ​ | 6,707,152 | ​ | ​ | ​ | ​ | ​ | 2,047,648 | ​ | ​ | ​ | ​ | ​ | 1,046,301 | ​ | ​ | ​ | ​ | ​ | 14,062,876 | ​ | ​
​ | Fiscal Year | ​ | ​ | Average SCT Non-PEO NEOs | ​ | ​ | Pension Deducted from SCT | ​ | ​ | Pension Service Value Added to SCT | ​ | ​ | Stock Awards Deducted from SCT | ​ | ​ | Fair Value of Equity Awards Granted during the Year and Remained Unvested at Year-End | ​ | ​ | Change in Fair Value of Unvested Equity Awards that Vested During the Year | ​ | ​ | Change in Fair Value of Unvested Equity Grants | ​ | ​ | Average CAP Non-PEO NEOs | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​
​ | 1 (2024) | ​ | ​ | ​ | ​ | 3,496,586 | ​ | ​ | ​ | ​ | ​ | -213,868 | ​ | ​ | ​ | ​ | ​ | 15,887 | ​ | ​ | ​ | ​ | ​ | -1,687,365 | ​ | ​ | ​ | ​ | ​ | 1,632,591 | ​ | ​ | ​ | ​ | ​ | -86,350 | ​ | ​ | ​ | ​ | ​ | -509,706 | ​ | ​ | ​ | ​ | ​ | 2,647,958 | ​ | ​
​ | 3 (2023) | ​ | ​ | ​ | ​ | 2,936,041 | ​ | ​ | ​ | ​ | ​ | -478,864 | ​ | ​ | ​ | ​ | ​ | 84,416 | ​ | ​ | ​ | ​ | ​ | -1,451,776 | ​ | ​ | ​ | ​ | ​ | 827,273 | ​ | ​ | ​ | ​ | ​ | -102,269 | ​ | ​ | ​ | ​ | ​ | -679,639 | ​ | ​ | ​ | ​ | ​ | 1,135,182 | ​ | ​
​ | 4 (2022) | ​ | ​ | ​ | ​ | 3,410,910 | ​ | ​ | ​ | ​ | ​ | -69,941 | ​ | ​ | ​ | ​ | ​ | 162,780 | ​ | ​ | ​ | ​ | ​ | -2,054,232 | ​ | ​ | ​ | ​ | ​ | 2,031,140 | ​ | ​ | ​ | ​ | ​ | -419,104 | ​ | ​ | ​ | ​ | ​ | -109,907 | ​ | ​ | ​ | ​ | ​ | 2,951,647 | ​ | ​
​ | 5 (2021) | ​ | ​ | ​ | ​ | 4,157,260 | ​ | ​ | ​ | ​ | ​ | -1,205,814 | ​ | ​ | ​ | ​ | ​ | 530,849 | ​ | ​ | ​ | ​ | ​ | -1,408,117 | ​ | ​ | ​ | ​ | ​ | 1,510,350 | ​ | ​ | ​ | ​ | ​ | -238,540 | ​ | ​ | ​ | ​ | ​ | 125,057 | ​ | ​ | ​ | ​ | ​ | 3,471,045 | ​ | ​
​ | 6 (2020) | ​ | ​ | ​ | ​ | 5,002,344 | ​ | ​ | ​ | ​ | ​ | -1,929,875 | ​ | ​ | ​ | ​ | ​ | 257,161 | ​ | ​ | ​ | ​ | ​ | -1,494,123 | ​ | ​ | ​ | ​ | ​ | 1,499,609 | ​ | ​ | ​ | ​ | ​ | 422,302 | ​ | ​ | ​ | ​ | ​ | 203,013 | ​ | ​ | ​ | ​ | ​ | 3,960,432 | ​ | ​
​ (a) The total pension benefit adjustments for each applicable year include the aggregate of two components: (i) the actuarially determined service cost for services rendered by the PEO and non-PEO NEOs during the applicable year (the “service cost”); and (ii) the entire cost of benefits granted in a plan amendment (or initiation) during the applicable year that are attributed by the benefit formula to services rendered in periods prior to the plan amendment or initiation (the “prior service cost”), in each case, calculated in accordance with U.S. GAAP ​
​ | Fiscal Year | ​ | ​ | Service Cost | ​ | ​ | Prior Service Cost | ​ | ​ | Total Pension Benefit Adjustments | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​
​ | PEO#1 (2024) | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​
​ | PEO#1 (2023) | ​ | ​ | ​ | ​ | 689,828 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 689,828 | ​ | ​
​ | PEO#1 (2022) | ​ | ​ | ​ | ​ | 429,463 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 429,463 | ​ | ​
​ | PEO#1 (2021) | ​ | ​ | ​ | ​ | 336,850 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 336,850 | ​ | ​
​ | PEO#2 (2021) | ​ | ​ | ​ | ​ | 845,242 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 845,242 | ​ | ​
​ | PEO#2 (2020) | ​ | ​ | ​ | ​ | 111,326 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 111,326 | ​ | ​
​ | Average Non-PEO NEO (2024) | ​ | ​ | ​ | ​ | 15,887 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 15,887 | ​ | ​
​ | Average Non-PEO NEO (2023) | ​ | ​ | ​ | ​ | 84,416 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 84,416 | ​ | ​
​ | Average Non-PEO NEO (2022) | ​ | ​ | ​ | ​ | 162,780 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 162,780 | ​ | ​
​ | Average Non-PEO NEO (2021) | ​ | ​ | ​ | ​ | 530,849 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 530,849 | ​ | ​
​ | Average Non-PEO NEO (2020) | ​ | ​ | ​ | ​ | 257,161 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 257,161 | ​ | ​
​ (b) For the periods covered, no individual equity awards were granted and vested in the same year and no dividends or other earnings were paid on outstanding and unvested awards. The valuation assumptions used to calculate the fair values of performance shares reflect the probable outcome of the performance conditions as of the applicable measuring date (or actual performance results approved by the Compensation Committee as of the applicable vesting date). Outstanding RSUs accrue dividend equivalent units in the form of additional common shares that are not distributed unless and until the underlying award vests and becomes payable. The value of dividend equivalent units is reflected in the values set forth above. |  |  |  |
Company Selected Measure Name | EPS |  |  |  |
Named Executive Officers, Footnote | (1) The PEOs for each year are as follows: ​ a. 2024, 2023, 2022 and 2021 — Joseph R. Nolan, Jr. ​ b. 2020 and 2021 — James J. Judge. Mr. Nolan became the Company’s Chief Executive Officer on May 5, 2021 ​ (2) The Non-PEO NEOs for each year are as follows: ​ a. 2024 — John Moreira, Paul Chodak, III, Susan Sgroi and Gregory B. Butler 2023 — John M. Moreira, Gregory B. Butler, Christine M. Carmody, James W. Hunt, III and Werner J. Schweiger ​ c. 2022 — John M. Moreira, Gregory B. Butler, Christine M. Carmody, Werner J. Schweiger, James J. Judge and Philip J. Lembo ​ d. 2021 — Philip J. Lembo, Werner J. Schweiger, Gregory B. Butler and Christine M. Carmody ​ e. 2020 — Philip J. Lembo, Werner J. Schweiger, Gregory B. Butler and Joseph R. Nolan |  |  |  |
Peer Group Issuers, Footnote | (3) The values disclosed in this TSR column represent the measurement period value of an investment of $100 in our units as of December 31, 2020, and then valued again on each of December 31, 2021, December 31, 2022, December 31, 2023 and December 31, 2024 as compared to the EEI Index, as disclosed in our Annual Report on Form 10-K for fiscal year ended 2024 pursuant to Item 201(e) of Regulation S-K |  |  |  |
Adjustment To PEO Compensation, Footnote | To calculate CAP for our PEOs and Non-PEO NEOs in the table above, the following amounts were deducted and added to the values as reported in the SCT:
​ | Fiscal Year | ​ | ​ | SCT Total PEO #1 | ​ | ​ | Pension Deducted from SCT | ​ | ​ | Pension Service Value Added to SCT | ​ | ​ | Stock Awards Deducted from SCT | ​ | ​ | Fair Value of Equity Awards Granted during the Year and Remained Unvested at Year-End | ​ | ​ | Change in Fair Value of Unvested Equity Awards that Vested During the Year | ​ | ​ | Change in Fair Value of Unvested Equity Grants | ​ | ​ | CAP PEO #1 | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​
​ | 1 (2024) | ​ | ​ | ​ | ​ | 13,578,154 | ​ | ​ | ​ | ​ | ​ | -2,188,733 | ​ | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​ | ​ | ​ | ​ | -7,510,128 | ​ | ​ | ​ | ​ | ​ | 7,266,337 | ​ | ​ | ​ | ​ | ​ | -308,543 | ​ | ​ | ​ | ​ | ​ | -2,778,136 | ​ | ​ | ​ | ​ | ​ | 9,503,340 | ​ | ​
​ | 2 (2023) | ​ | ​ | ​ | ​ | 18,885,577 | ​ | ​ | ​ | ​ | ​ | -7,832,472 | ​ | ​ | ​ | ​ | ​ | 689,828 | ​ | ​ | ​ | ​ | ​ | -8,018,396 | ​ | ​ | ​ | ​ | ​ | 6,023,948 | ​ | ​ | ​ | ​ | ​ | -182,331 | ​ | ​ | ​ | ​ | ​ | -2,136,906 | ​ | ​ | ​ | ​ | ​ | 7,429,247 | ​ | ​
​ | 3 (2022) | ​ | ​ | ​ | ​ | 12,959,134 | ​ | ​ | ​ | ​ | ​ | -2,143,443 | ​ | ​ | ​ | ​ | ​ | 429,463 | ​ | ​ | ​ | ​ | ​ | -6,825,923 | ​ | ​ | ​ | ​ | ​ | 6,749,195 | ​ | ​ | ​ | ​ | ​ | -235,802 | ​ | ​ | ​ | ​ | ​ | -74,557 | ​ | ​ | ​ | ​ | ​ | 10,858,066 | ​ | ​
​ | 4 (2021) | ​ | ​ | ​ | ​ | 6,467,078 | ​ | ​ | ​ | ​ | ​ | -1,705,782 | ​ | ​ | ​ | ​ | ​ | 336,850 | ​ | ​ | ​ | ​ | ​ | -1,441,650 | ​ | ​ | ​ | ​ | ​ | 1,546,319 | ​ | ​ | ​ | ​ | ​ | -201,335 | ​ | ​ | ​ | ​ | ​ | 118,712 | ​ | ​ | ​ | ​ | ​ | 5,120,192 | ​ | ​
​ | Fiscal Year | ​ | ​ | SCT Total PEO #2 | ​ | ​ | Pension Deducted from SCT | ​ | ​ | Pension Service Value Added to SCT | ​ | ​ | Stock Awards Deducted from SCT | ​ | ​ | Fair Value of Equity Awards Granted during the Year and Remained Unvested at Year-End | ​ | ​ | Change in Fair Value of Unvested Equity Awards that Vested During the Year | ​ | ​ | Change in Fair Value of Unvested Equity Grants | ​ | ​ | CAP PEO #2 | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​
​ | (2021) | ​ | ​ | ​ | ​ | 10,220,941 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 845,242 | ​ | ​ | ​ | ​ | ​ | -6,786,337 | ​ | ​ | ​ | ​ | ​ | 7,279,051 | ​ | ​ | ​ | ​ | ​ | -1,266,246 | ​ | ​ | ​ | ​ | ​ | 617,814 | ​ | ​ | ​ | ​ | ​ | 10,910,465 | ​ | ​
​ | (2020) | ​ | ​ | ​ | ​ | 14,575,276 | ​ | ​ | ​ | ​ | ​ | -3,742,215 | ​ | ​ | ​ | ​ | ​ | 111,326 | ​ | ​ | ​ | ​ | ​ | -6,682,612 | ​ | ​ | ​ | ​ | ​ | 6,707,152 | ​ | ​ | ​ | ​ | ​ | 2,047,648 | ​ | ​ | ​ | ​ | ​ | 1,046,301 | ​ | ​ | ​ | ​ | ​ | 14,062,876 | ​ | ​
(a) The total pension benefit adjustments for each applicable year include the aggregate of two components: (i) the actuarially determined service cost for services rendered by the PEO and non-PEO NEOs during the applicable year (the “service cost”); and (ii) the entire cost of benefits granted in a plan amendment (or initiation) during the applicable year that are attributed by the benefit formula to services rendered in periods prior to the plan amendment or initiation (the “prior service cost”), in each case, calculated in accordance with U.S. GAAP ​
​ | Fiscal Year | ​ | ​ | Service Cost | ​ | ​ | Prior Service Cost | ​ | ​ | Total Pension Benefit Adjustments | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​
​ | PEO#1 (2024) | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​
​ | PEO#1 (2023) | ​ | ​ | ​ | ​ | 689,828 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 689,828 | ​ | ​
​ | PEO#1 (2022) | ​ | ​ | ​ | ​ | 429,463 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 429,463 | ​ | ​
​ | PEO#1 (2021) | ​ | ​ | ​ | ​ | 336,850 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 336,850 | ​ | ​
​ | PEO#2 (2021) | ​ | ​ | ​ | ​ | 845,242 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 845,242 | ​ | ​
​ | PEO#2 (2020) | ​ | ​ | ​ | ​ | 111,326 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 111,326 | ​ | ​
​ | Average Non-PEO NEO (2024) | ​ | ​ | ​ | ​ | 15,887 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 15,887 | ​ | ​
​ | Average Non-PEO NEO (2023) | ​ | ​ | ​ | ​ | 84,416 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 84,416 | ​ | ​
​ | Average Non-PEO NEO (2022) | ​ | ​ | ​ | ​ | 162,780 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 162,780 | ​ | ​
​ | Average Non-PEO NEO (2021) | ​ | ​ | ​ | ​ | 530,849 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 530,849 | ​ | ​
​ | Average Non-PEO NEO (2020) | ​ | ​ | ​ | ​ | 257,161 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 257,161 | ​ | ​
​ (b) For the periods covered, no individual equity awards were granted and vested in the same year and no dividends or other earnings were paid on outstanding and unvested awards. The valuation assumptions used to calculate the fair values of performance shares reflect the probable outcome of the performance conditions as of the applicable measuring date (or actual performance results approved by the Compensation Committee as of the applicable vesting date). Outstanding RSUs accrue dividend equivalent units in the form of additional common shares that are not distributed unless and until the underlying award vests and becomes payable. The value of dividend equivalent units is reflected in the values set forth above. |  |  |  |
Non-PEO NEO Average Total Compensation Amount | $ 3,496,586 | $ 2,936,041 | $ 3,410,910 | $ 4,157,260 | $ 5,002,344
Non-PEO NEO Average Compensation Actually Paid Amount | $ 2,647,958 | 1,135,182 | 2,951,647 | 3,471,045 | 3,960,432
Adjustment to Non-PEO NEO Compensation Footnote | To calculate CAP for our PEOs and Non-PEO NEOs in the table above, the following amounts were deducted and added to the values as reported in the SCT:
​ | Fiscal Year | ​ | ​ | Average SCT Non-PEO NEOs | ​ | ​ | Pension Deducted from SCT | ​ | ​ | Pension Service Value Added to SCT | ​ | ​ | Stock Awards Deducted from SCT | ​ | ​ | Fair Value of Equity Awards Granted during the Year and Remained Unvested at Year-End | ​ | ​ | Change in Fair Value of Unvested Equity Awards that Vested During the Year | ​ | ​ | Change in Fair Value of Unvested Equity Grants | ​ | ​ | Average CAP Non-PEO NEOs | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​ | ​ | e | ​ | ​ | f | ​ | ​ | g | ​ | ​ | h | ​ | ​ | i | ​
​ | 1 (2024) | ​ | ​ | ​ | ​ | 3,496,586 | ​ | ​ | ​ | ​ | ​ | -213,868 | ​ | ​ | ​ | ​ | ​ | 15,887 | ​ | ​ | ​ | ​ | ​ | -1,687,365 | ​ | ​ | ​ | ​ | ​ | 1,632,591 | ​ | ​ | ​ | ​ | ​ | -86,350 | ​ | ​ | ​ | ​ | ​ | -509,706 | ​ | ​ | ​ | ​ | ​ | 2,647,958 | ​ | ​
​ | 3 (2023) | ​ | ​ | ​ | ​ | 2,936,041 | ​ | ​ | ​ | ​ | ​ | -478,864 | ​ | ​ | ​ | ​ | ​ | 84,416 | ​ | ​ | ​ | ​ | ​ | -1,451,776 | ​ | ​ | ​ | ​ | ​ | 827,273 | ​ | ​ | ​ | ​ | ​ | -102,269 | ​ | ​ | ​ | ​ | ​ | -679,639 | ​ | ​ | ​ | ​ | ​ | 1,135,182 | ​ | ​
​ | 4 (2022) | ​ | ​ | ​ | ​ | 3,410,910 | ​ | ​ | ​ | ​ | ​ | -69,941 | ​ | ​ | ​ | ​ | ​ | 162,780 | ​ | ​ | ​ | ​ | ​ | -2,054,232 | ​ | ​ | ​ | ​ | ​ | 2,031,140 | ​ | ​ | ​ | ​ | ​ | -419,104 | ​ | ​ | ​ | ​ | ​ | -109,907 | ​ | ​ | ​ | ​ | ​ | 2,951,647 | ​ | ​
​ | 5 (2021) | ​ | ​ | ​ | ​ | 4,157,260 | ​ | ​ | ​ | ​ | ​ | -1,205,814 | ​ | ​ | ​ | ​ | ​ | 530,849 | ​ | ​ | ​ | ​ | ​ | -1,408,117 | ​ | ​ | ​ | ​ | ​ | 1,510,350 | ​ | ​ | ​ | ​ | ​ | -238,540 | ​ | ​ | ​ | ​ | ​ | 125,057 | ​ | ​ | ​ | ​ | ​ | 3,471,045 | ​ | ​
​ | 6 (2020) | ​ | ​ | ​ | ​ | 5,002,344 | ​ | ​ | ​ | ​ | ​ | -1,929,875 | ​ | ​ | ​ | ​ | ​ | 257,161 | ​ | ​ | ​ | ​ | ​ | -1,494,123 | ​ | ​ | ​ | ​ | ​ | 1,499,609 | ​ | ​ | ​ | ​ | ​ | 422,302 | ​ | ​ | ​ | ​ | ​ | 203,013 | ​ | ​ | ​ | ​ | ​ | 3,960,432 | ​ | ​
​ (a) The total pension benefit adjustments for each applicable year include the aggregate of two components: (i) the actuarially determined service cost for services rendered by the PEO and non-PEO NEOs during the applicable year (the “service cost”); and (ii) the entire cost of benefits granted in a plan amendment (or initiation) during the applicable year that are attributed by the benefit formula to services rendered in periods prior to the plan amendment or initiation (the “prior service cost”), in each case, calculated in accordance with U.S. GAAP ​
​ | Fiscal Year | ​ | ​ | Service Cost | ​ | ​ | Prior Service Cost | ​ | ​ | Total Pension Benefit Adjustments | ​
​ | a | ​ | ​ | b | ​ | ​ | c | ​ | ​ | d | ​
​ | PEO#1 (2024) | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 1,444,389 | ​ | ​
​ | PEO#1 (2023) | ​ | ​ | ​ | ​ | 689,828 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 689,828 | ​ | ​
​ | PEO#1 (2022) | ​ | ​ | ​ | ​ | 429,463 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 429,463 | ​ | ​
​ | PEO#1 (2021) | ​ | ​ | ​ | ​ | 336,850 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 336,850 | ​ | ​
​ | PEO#2 (2021) | ​ | ​ | ​ | ​ | 845,242 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 845,242 | ​ | ​
​ | PEO#2 (2020) | ​ | ​ | ​ | ​ | 111,326 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 111,326 | ​ | ​
​ | Average Non-PEO NEO (2024) | ​ | ​ | ​ | ​ | 15,887 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 15,887 | ​ | ​
​ | Average Non-PEO NEO (2023) | ​ | ​ | ​ | ​ | 84,416 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 84,416 | ​ | ​
​ | Average Non-PEO NEO (2022) | ​ | ​ | ​ | ​ | 162,780 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 162,780 | ​ | ​
​ | Average Non-PEO NEO (2021) | ​ | ​ | ​ | ​ | 530,849 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 530,849 | ​ | ​
​ | Average Non-PEO NEO (2020) | ​ | ​ | ​ | ​ | 257,161 | ​ | ​ | ​ | ​ | ​ | 0 | ​ | ​ | ​ | ​ | ​ | 257,161 | ​ | ​
​ (b) For the periods covered, no individual equity awards were granted and vested in the same year and no dividends or other earnings were paid on outstanding and unvested awards. The valuation assumptions used to calculate the fair values of performance shares reflect the probable outcome of the performance conditions as of the applicable measuring date (or actual performance results approved by the Compensation Committee as of the applicable vesting date). Outstanding RSUs accrue dividend equivalent units in the form of additional common shares that are not distributed unless and until the underlying award vests and becomes payable. The value of dividend equivalent units is reflected in the values set forth above. |  |  |  |
Compensation Actually Paid vs. Total Shareholder Return | Relationship Between CAP for the PEOs and Non-PEO NEOs (Average) vs. TSR ​ |  |  |  |
Compensation Actually Paid vs. Net Income | Relationship Between CAP for the PEOs and Non-PEO NEOs (Average) vs. Net Income ​ ​ |  |  |  |
Compensation Actually Paid vs. Company Selected Measure | Relationship Between CAP for the PEOs and Non-PEO NEOs (Average) vs. Non-GAAP EPS ​ |  |  |  |
Total Shareholder Return Vs Peer Group | Relationship Between CAP for the PEOs and Non-PEO NEOs (Average) vs. TSR |  |  |  |
Tabular List, Table |
​ | ​ | ​ | ​ | Most Important Performance Measures | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | Earnings Per Share | ​ | ​
​ | ​ | ​ | ​ | Dividend Growth | ​ | ​
​ | ​ | ​ | ​ | Total Shareholder Return | ​ | ​
​ | ​ | ​ | ​ | Reliability | ​ | ​
​ | ​ | ​ | ​ | Restoration | ​ | ​
​ | ​ | ​ | ​ | Strategic Growth Initiatives | ​ | ​
Total Shareholder Return Amount | $ 80 | 82 | 107 | 113 | 105
Peer Group Total Shareholder Return Amount | 127 | 107 | 117 | 116 | 99
Net Income (Loss) | $ 811.7 | $ (442.2) | $ 1,404.9 | $ 1,220.5 | $ 1,205.2
Company Selected Measure Amount | 4.57 | 4.34 | 4.09 | 3.86 | 3.64
PEO Name | Joseph R. Nolan, Jr. |  |  |  |
Measure:: 1 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Earnings Per Share |  |  |  |
Non-GAAP Measure Description | (4) Set forth in Footnote 1 on page 39 and Exhibit A to the CD&A is a full description of how non-GAAP EPS was determined. The Company believes non-GAAP EPS is a very important measure to investors and which is indicative of Company performance; accordingly, it represents a significant factor in determining both annual and long term executive compensation, though as noted the Compensation Committee determined that due to the disappointing performance in our 2024 stock price, the Committee reduced payout for the EPS-based goal in our 2024 annual incentive plan to 75 percent from |  |  |  |
Measure:: 2 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Dividend Growth |  |  |  |
Measure:: 3 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Total Shareholder Return |  |  |  |
Measure:: 4 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Reliability |  |  |  |
Measure:: 5 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Restoration |  |  |  |
Measure:: 6 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Strategic Growth Initiatives |  |  |  |
Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | $ 15,887 |  |  |  |
Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 15,887 |  |  |  |
Pension Adjustments Prior Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 0 |  |  |  |
Joseph Nolan [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
PEO Total Compensation Amount | 13,578,154 | $ 18,885,577 | $ 12,959,134 | $ 6,467,078 |
PEO Actually Paid Compensation Amount | 9,503,340 | 7,429,247 | 10,858,066 | 5,120,192 |
Joseph Nolan [Member] | Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 1,444,389 | 689,828 | 429,463 | 336,850 |
Joseph Nolan [Member] | Aggregate Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (2,188,733) | (7,832,472) | (2,143,443) | (1,705,782) |
Joseph Nolan [Member] | Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 1,444,389 | 689,828 | 429,463 | 336,850 |
Joseph Nolan [Member] | Pension Adjustments Prior Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 0 | 0 | 0 | 0 |
Joseph Nolan [Member] | Equity Awards Adjustments |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (7,510,128) | (8,018,396) | (6,825,923) | (1,441,650) |
Joseph Nolan [Member] | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 7,266,337 | 6,023,948 | 6,749,195 | 1,546,319 |
Joseph Nolan [Member] | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (2,778,136) | (2,136,906) | (74,557) | 118,712 |
Joseph Nolan [Member] | Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (308,543) | (182,331) | (235,802) | (201,335) |
James Judge [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
PEO Total Compensation Amount |  |  |  | 10,220,941 | $ 14,575,276
PEO Actually Paid Compensation Amount |  |  |  | 10,910,465 | 14,062,876
James Judge [Member] | Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | 845,242 | 111,326
James Judge [Member] | Aggregate Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | 0 | (3,742,215)
James Judge [Member] | Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | 845,242 | 111,326
James Judge [Member] | Pension Adjustments Prior Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | 0 | 0
James Judge [Member] | Equity Awards Adjustments |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | (6,786,337) | (6,682,612)
James Judge [Member] | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | 7,279,051 | 6,707,152
James Judge [Member] | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | 617,814 | 1,046,301
James Judge [Member] | Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  |  | (1,266,246) | 2,047,648
Non-PEO NEO | Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 15,887 | 84,416 | 162,780 | 530,849 | 257,161
Non-PEO NEO | Aggregate Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (213,868) | (478,864) | (69,941) | (1,205,814) | (1,929,875)
Non-PEO NEO | Pension Adjustments Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 84,416 | 162,780 | 530,849 | 257,161
Non-PEO NEO | Pension Adjustments Prior Service Cost |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 0 | 0 | 0 | 0
Non-PEO NEO | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 1,632,591 | 827,273 | 2,031,140 | 1,510,350 | 1,499,609
Non-PEO NEO | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (509,706) | (679,639) | (109,907) | 125,057 | 203,013
Non-PEO NEO | Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (86,350) | (102,269) | (419,104) | (238,540) | 422,302
Non-PEO NEO | Total Net Adjustments For Equity Awards [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | $ (1,687,365) | $ (1,451,776) | $ (2,054,232) | $ (1,408,117) | $ (1,494,123)

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_AdjToCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_AdjToNonPeoNeoCompFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_AdjToPeoCompFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_CoSelectedMeasureAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_CoSelectedMeasureName
Namespace Prefix: | ecd_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 5 -Subparagraph iii + Details
Name: | ecd_CompActuallyPaidVsCoSelectedMeasureTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 5 -Subparagraph ii + Details
Name: | ecd_CompActuallyPaidVsNetIncomeTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 5 -Subparagraph i + Details
Name: | ecd_CompActuallyPaidVsTotalShareholderRtnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_MeasureName
Namespace Prefix: | ecd_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_NamedExecutiveOfficersFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_NonGaapMeasureDescriptionTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iii + Details
Name: | ecd_NonPeoNeoAvgCompActuallyPaidAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph ii + Details
Name: | ecd_NonPeoNeoAvgTotalCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iv + Details
Name: | ecd_PeerGroupIssuersFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iv + Details
Name: | ecd_PeerGroupTotalShareholderRtnAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iii + Details
Name: | ecd_PeoActuallyPaidCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_PeoName
Namespace Prefix: | ecd_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph ii + Details
Name: | ecd_PeoTotalCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 1 + Details
Name: | ecd_PvpTable
Namespace Prefix: | ecd_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 1 + Details
Name: | ecd_PvpTableTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 6 + Details
Name: | ecd_TabularListTableTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iv + Details
Name: | ecd_TotalShareholderRtnAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 5 -Subparagraph iv + Details
Name: | ecd_TotalShareholderRtnVsPeerGroupTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-9 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 60 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476176/805-60-65-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 323 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478666/740-323-65-2 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(20)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 323 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481687/323-10-50-3 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 28 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-28 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482765/220-10-50-6 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-3 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-1 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480175/815-40-65-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-8 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-11 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-11 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-4 Reference 17: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-10 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section 45 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479105/946-220-45-7 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(18)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(1)(d)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 23: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(ii)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(iii)(A)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iii)(A)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iii)(B)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 260 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 60B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 205 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483499/205-20-50-7 Reference 34: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B Reference 37: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(22)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ecd_MeasureAxis=1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=3
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=4
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=5
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=6
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_AggtChngPnsnValInSummryCompstnTblForAplblYrMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_PnsnAdjsSvcCstMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_PnsnAdjsPrrSvcCstMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_IndividualAxis=es_JosephNolanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_AggtPnsnAdjsSvcCstMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_EqtyAwrdsAdjsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_VstngDtFrValOfEqtyAwrdsGrntdAndVstdInCvrdYrMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_IndividualAxis=es_JamesJudgeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_ExecutiveCategoryAxis=ecd_NonPeoNeoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=es_NetAdjustmentsForEquityAwardsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |