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Pay vs Performance Disclosure - USD ($) | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Pay vs Performance Disclosure |  |  |  |  |
Pay vs Performance Disclosure, Table |  |
|  |  |  |  |  | Average Summary |  | Average |  | Value of Initial Fixed $100 Investment Based On: |  |  |  |
Year (a) |  | Summary Compensation Table Total for CEO (b) |  | Compensation Actually Paid to CEO (c) |  | Compensation Table Total for non-CEO NEOs (d) |  | Compensation Actually Paid to non-CEO NEOs (e) |  | Total Shareholder Return (f) |  | Peer Group Total Shareholder Return (g) |  | Net Income (In Millions) (h) |  | Income Before Income Taxes (In Millions) (i)
2023 |  | $ | 1,758,814 |  |  | $ | 1,414,050 |  |  | $ | 673,736 |  |  | $ | 673,736 |  |  | $ | 109.30 |  |  | $ | 130.30 |  |  | $ | 31.5 |  |  | $ | 32.6 |
2022 |  | $ | 1,154,726 |  |  | $ | 38,867 |  |  | $ | 452,477 |  |  | $ | 284,597 |  |  | $ | 128.86 |  |  | $ | 120.09 |  |  | $ | 42.4 |  |  | $ | 45.7 |
2021 |  | $ | 1,290,444 |  |  | $ | 3,173,051 |  |  | $ | 490,567 |  |  | $ | 782,328 |  |  | $ | 194.55 |  |  | $ | 132.92 |  |  | $ | 36.5 |  |  | $ | 31.1 |
2020 |  | $ | 1,781,494 |  |  | $ | 1,714,156 |  |  | $ | 677,013 |  |  | $ | 526,936 |  |  | $ | 115.79 |  |  | $ | 101.42 |  |  | $ | 38.4 |  |  | $ | 34.3 |
Column (b) Reflects compensation amounts reported in the “Summary Compensation Table” for our CEO, Dennis Doll, for the respective years shown. Column (c) “Compensation actually paid” to our CEO in each of 2023, 2022, 2021, and 2020 reflects the respective amounts set forth in column (b) of the compensation table above, adjusted as set forth in the compensation calculation table below, as determined in accordance with SEC rules. The dollar amounts reflected in column (b) of the table above do not reflect the actual amount of compensation earned by or paid to our CEO during the applicable year. For information regarding the decisions made by our Compensation Committee in regards to the CEO’s compensation for each fiscal year, please see the CD&A sections of the Proxy Statements reporting pay for the fiscal years covered in the table above. The aggregate change in actuarial present value of accumulated benefit under pension plans reflects the amount reported for the applicable year in the Summary Compensation Table. Column (d) Reflects compensation information for our NEOs other than the CEO as described in the CD&A of this Proxy Statement. 2023 A. Bruce O’Connor, Jay L. Kooper, Georgia M. Simpson, Robert K. Fullagar 2022: A. Bruce O’Connor, Jay L. Kooper, Georgia M. Simpson, Robert K. Fullagar 2021: A. Bruce O’Connor, Bernadette M. Sohler, Jay L. Kooper, Lorrie B. Ginegaw 2020: A. Bruce O’Connor, Bernadette M. Sohler, Jay L. Kooper, Lorrie B. Ginegaw Column (e) Average “compensation actually paid” for our non-CEO NEOs in each of 2023, 2022, 2021, and 2020 reflects the respective amounts set forth in column (d) of the table above, adjusted as set forth in the compensation calculation table below, as determined in accordance with SEC rules. The dollar amounts reflected in column (d) of the table above do not reflect the actual amount of compensation earned by or paid to our non-CEO NEOs during the applicable year. For information regarding the decisions made by our Compensation Committee in regards to the non-CEO NEOs compensation for each fiscal year, please see the CD&A sections of the Proxy Statements reporting pay for the fiscal years covered in the table above. Column (f) For the relevant fiscal year, represents the cumulative total shareholder return (TSR) of Middlesex for the measurement periods ending on December 31 of each of 2023, 2022 and 2021, respectively. Column (g) For the relevant fiscal year, represents the cumulative TSR of the Peer Group for the measurement periods ending on December 31 of each of 2023, 2022, 2021, and 2020, respectively. Peer Group companies currently include American States Water Company, Artesian Resources Corp., California Water Service Group, Global Water Resources Inc., SJW Corp., and York Water Company. Column (h) Source: Company’s Annual Report on Form 10-K for each respective year. Column (i) Source: Company’s Annual Report on Form 10-K for each respective year. |  |  |
Named Executive Officers, Footnote |  | Reflects compensation amounts reported in the “Summary Compensation Table” for our CEO, Dennis Doll, for the respective years shown. |  |  |
Peer Group Issuers, Footnote |  | For the relevant fiscal year, represents the cumulative total shareholder return (TSR) of Middlesex for the measurement periods ending on December 31 of each of 2023, 2022 and 2021, respectively. |  |  |
PEO Total Compensation Amount | [1] | $ 1,758,814 | $ 1,154,726 | $ 1,290,444 | $ 1,781,494
PEO Actually Paid Compensation Amount | [2] | $ 1,414,050 | 38,867 | 3,173,051 | 1,714,156
Adjustment To PEO Compensation, Footnote |  |
Year |  | Summary Compensation Table Total for CEO |  | Summary Compensation Table Equity Awards for CEO |  | Equity Awards Adjustment for CEO |  | Summary Compensation Table Change in Pension Value for CEO |  | Pension Service Cost Adjustment for CEO |  | Total Compensation Actually Paid to CEO
2023 |  | $ | 1,758,814 |  |  | $ | — |  |  | $ | 21,252 |  |  | $ | — |  |  | $ | 264,510 |  |  | $ | 1,414,050 |
2022 |  | $ | 1,154,726 |  |  | $ | (400,000 | ) |  | $ | (1,008,164 | ) |  | $ | (630,526 | ) |  | $ | 292,314 |  |  | $ | 38,876 |
2021 |  | $ | 1,290,444 |  |  | $ | (400,000 | ) |  | $ | 2,176,122 |  |  | $ | (174,119 | ) |  | $ | 280,604 |  |  | $ | 3,173,051 |
2020 |  | $ | 1,781,494 |  |  | $ | (400,000 | ) |  | $ | 758,543 |  |  | $ | (679,154 | ) |  | $ | 253,273 |  |  | $ | 1,714,156 |
Fair Value of Equity Awards for CEO |  | 2023 |  | 2022 |  | 2021 |  | 2020
Year End Fair Value of Current Year Equity Award |  | $ | 338,140 |  |  | $ | 299,182 |  |  | $ | 608,959 |  |  | $ | 403,368 |
Year End Change in Fair Value of Prior Year Equity Awards |  | $ | (307,889 | ) |  | $ | (1,184,082 | ) |  | $ | 1,507,984 |  |  | $ | 311,473 |
Change in Fair Value of Prior Year Equity Awards Vesting in Current Year |  | $ | (8,999 | ) |  | $ | (123,264 | ) |  | $ | 59,179 |  |  | $ | 43,702 |
Total Equity Awards Adjustments for CEO |  | $ | 21,252 |  |  | $ | (1,008,164 | ) |  | $ | 2,176,122 |  |  | $ | 758,543 |
Non-PEO NEO Average Total Compensation Amount | [3] | $ 673,736 | 452,477 | 490,567 | 677,013
Non-PEO NEO Average Compensation Actually Paid Amount | [4] | $ 673,736 | 284,597 | 782,328 | 526,936
Adjustment to Non-PEO NEO Compensation Footnote |  |
Year |  | Average Summary Compensation Table Total for non-CEO NEOs |  | Average Summary Compensation Table Equity Awards for non-CEO NEOs |  | Average Equity Awards Adjustment for non-CEO NEOs |  | Average Summary Compensation Table Change in Pension Value for non-CEO NEOs |  | Average Pension Service Cost Adjustment for non-CEO NEOs |  | Average Total Compensation Actually Paid to non-CEO NEOs
2023 |  | $ | 673,736 |  |  | $ | (45,064 | ) |  | $ | 22,748 |  |  | $ | (196,877 | ) |  | $ | 12,926 |  |  | $ | 467,470 |
2022 |  | $ | 452,477 |  |  | $ | (92,500 | ) |  | $ | (120,479 | ) |  | $ | — |  |  | $ | 45,098 |  |  | $ | 284,597 |
2021 |  | $ | 490,567 |  |  | $ | (88,750 | ) |  | $ | 390,457 |  |  | $ | (78,407 | ) |  | $ | 68,461 |  |  | $ | 782,328 |
2020 |  | $ | 677,013 |  |  | $ | (88,750 | ) |  | $ | 153,174 |  |  | $ | (273,752 | ) |  | $ | 59,252 |  |  | $ | 526,936 |
Fair Value of Average Equity Awards for non-CEO NEOs |  | 2023 |  |  | 2022 |  | 2021
Year End Fair Value of Current Year Equity Award |  | $ | 78,203 |  |  | $ | 67,342 |  |  | $ | 135,097 |
Year End Change in Fair Value of Prior Year Equity Awards |  | $ | (54,533 | ) |  | $ | (175,221 | ) |  | $ | 246,026 |
Change in Fair Value of Prior Year Equity Awards Vesting in Current Year |  | $ | (922 | ) |  | $ | (12,600 | ) |  | $ | 9,334 |
Total Equity Awards Adjustments non-CEO NEOs |  | $ | 22,748 |  |  | $ | (120,479 | ) |  | $ | 390,457 |
Compensation Actually Paid vs. Total Shareholder Return |  |  |  |  |
Compensation Actually Paid vs. Net Income |  |  |  |  |
Tabular List, Table |  | Pay for Performance Alignment The Company has identified Income Before Taxes, as referenced in the table at the top of page 32, as the most important financial performance measure. As income taxes are largely a function of taxable income, management has a greater ability to drive financial performance affecting those income statement line items, which are separate and apart from income taxes, than income taxes themselves. Listed below are the financial performance measures, which in our assessment, represent additional important financial performance measures we use to link compensation actually paid to our NEOs, for 2023, to company performance.
| • | Return on Average Common Equity
| • | Net Income
| • | TSR
Total Shareholder Return Amount | [5] | $ 109.3 | 128.86 | 194.55 | 115.79
Peer Group Total Shareholder Return Amount | [6] | 130.3 | 120.09 | 132.92 | 101.42
Net Income (Loss) | [7] | $ 31,500,000 | 42,400,000 | 36,500,000 | 38,400,000
PEO Name |  | Dennis Doll |  |  |
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest | [8] | $ 32,600,000 | 45,700,000 | 31,100,000 | 34,300,000
Measure:: 1 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name |  | Return on Average Common Equity |  |  |
Measure:: 2 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name |  | Net Income |  |  |
Measure:: 3 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name |  | TSR |  |  |
CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | $ 21,252 | (1,008,164) | 2,176,122 | 758,543
CEO [Member] | Summary Compensation Table Total for CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 1,758,814 | 1,154,726 | 1,290,444 | 1,781,494
CEO [Member] | Summary Compensation Table Equity Awards for CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | (400,000) | (400,000) | (400,000)
CEO [Member] | Equity Awards Adjustment for CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 21,252 | (1,008,164) | 2,176,122 | 758,543
CEO [Member] | Summary Compensation Table Change in Pension Value for CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | (630,526) | (174,119) | (679,154)
CEO [Member] | Pension Service Cost Adjustment for CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 264,510 | 292,314 | 280,604 | 253,273
CEO [Member] | Total Compensation Actually Paid to CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 1,414,050 | 38,876 | 3,173,051 | 1,714,156
CEO [Member] | Year End Fair Value of Current Year Equity Award [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 338,140 | 299,182 | 608,959 | 403,368
CEO [Member] | Year End Change in Fair Value of Prior Year Equity Awards [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | (307,889) | (1,184,082) | 1,507,984 | 311,473
CEO [Member] | Change in Fair Value of Prior Year Equity Awards Vesting in Current Year [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | (8,999) | (123,264) | 59,179 | 43,702
Non-CEO [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 22,748 | (120,479) | 390,457 |
Non-CEO [Member] | Year End Fair Value of Current Year Equity Award [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 78,203 | 67,342 | 135,097 |
Non-CEO [Member] | Year End Change in Fair Value of Prior Year Equity Awards [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | (54,533) | (175,221) | 246,026 |
Non-CEO [Member] | Change in Fair Value of Prior Year Equity Awards Vesting in Current Year [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | (922) | (12,600) | 9,334 |
Non-CEO [Member] | Average Summary Compensation Table Total for non-CEO NEOs [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 673,736 | 452,477 | 490,567 | 677,013
Non-CEO [Member] | Average Summary Compensation Table Equity Awards for non-CEO NEOs [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | (45,064) | (92,500) | (88,750) | (88,750)
Non-CEO [Member] | Average Equity Awards Adjustment for non-CEO NEOs [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 22,748 | (120,479) | 390,457 | 153,174
Non-CEO [Member] | Average Summary Compensation Table Change in Pension Value for non-CEO NEOs [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | (196,877) |  | (78,407) | (273,752)
Non-CEO [Member] | Average Pension Service Cost Adjustment for non-CEO NEOs [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | 12,926 | 45,098 | 68,461 | 59,252
Non-CEO [Member] | Average Total Compensation Actually Paid to non-CEO NEOs [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  | $ 467,470 | $ 284,597 | $ 782,328 | $ 526,936
[1] | Reflects compensation amounts reported in the “Summary Compensation Table” for our CEO, Dennis Doll, for the respective years shown.
[2] | “Compensation actually paid” to our CEO in each of 2023, 2022, 2021, and 2020 reflects the respective amounts set forth in column (b) of the compensation table above, adjusted as set forth in the compensation calculation table below, as determined in accordance with SEC rules. The dollar amounts reflected in column (b) of the table above do not reflect the actual amount of compensation earned by or paid to our CEO during the applicable year. For information regarding the decisions made by our Compensation Committee in regards to the CEO’s compensation for each fiscal year, please see the CD&A sections of the Proxy Statements reporting pay for the fiscal years covered in the table above. The aggregate change in actuarial present value of accumulated benefit under pension plans reflects the amount reported for the applicable year in the Summary Compensation Table.
[3] | Reflects compensation information for our NEOs other than the CEO as described in the CD&A of this Proxy Statement. 2023 A. Bruce O’Connor, Jay L. Kooper, Georgia M. Simpson, Robert K. Fullagar 2022: A. Bruce O’Connor, Jay L. Kooper, Georgia M. Simpson, Robert K. Fullagar 2021: A. Bruce O’Connor, Bernadette M. Sohler, Jay L. Kooper, Lorrie B. Ginegaw 2020: A. Bruce O’Connor, Bernadette M. Sohler, Jay L. Kooper, Lorrie B. Ginegaw
[4] | Average “compensation actually paid” for our non-CEO NEOs in each of 2023, 2022, 2021, and 2020 reflects the respective amounts set forth in column (d) of the table above, adjusted as set forth in the compensation calculation table below, as determined in accordance with SEC rules. The dollar amounts reflected in column (d) of the table above do not reflect the actual amount of compensation earned by or paid to our non-CEO NEOs during the applicable year. For information regarding the decisions made by our Compensation Committee in regards to the non-CEO NEOs compensation for each fiscal year, please see the CD&A sections of the Proxy Statements reporting pay for the fiscal years covered in the table above.
[5] | For the relevant fiscal year, represents the cumulative total shareholder return (TSR) of Middlesex for the measurement periods ending on December 31 of each of 2023, 2022 and 2021, respectively.
[6] | Column (g) For the relevant fiscal year, represents the cumulative TSR of the Peer Group for the measurement periods ending on December 31 of each of 2023, 2022, 2021, and 2020, respectively. Peer Group companies currently include American States Water Company, Artesian Resources Corp., California Water Service Group, Global Water Resources Inc., SJW Corp., and York Water Company.
[7] | Source: Company’s Annual Report on Form 10-K for each respective year.
[8] | Source: Company’s Annual Report on Form 10-K for each respective year.

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