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Employee Benefits (Tables) | 12 Months Ended
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Dec. 31, 2023
Retirement Benefits [Abstract] |
Reconciliation of the changes in the plans' benefit obligations and fair value of assets | The following tables provide a reconciliation of the changes in our plans' benefit obligations and fair value of assets:
|  | Pension Benefits |  | OPEB Benefits
(in millions) |  | 2023 |  | 2022 |  | 2023 |  | 2022
Change in benefit obligation |  |  |  |  |  |  |  |
Obligation at January 1 |  | $ | 2,315.9 |  |  | $ | 3,136.6 |  |  | $ | 402.3 |  |  | $ | 530.2 |
Service cost |  | 24.0 |  |  | 50.8 |  |  | 9.8 |  |  | 14.3 |
Interest cost |  | 122.3 |  |  | 91.8 |  |  | 21.6 |  |  | 15.4 |
Participant contributions |  | — |  |  | — |  |  | 11.8 |  |  | 12.5 |
Plan amendments |  | — |  |  | — |  |  | — |  |  | 0.2 |
Actuarial (gain) loss |  | 81.9 |  |  | (682.3) |  |  | 45.9 |  |  | (127.9) |
Benefit payments |  | (191.7) |  |  | (281.0) |  |  | (46.0) |  |  | (45.7) |
Federal subsidy on benefits paid |  | N/A |  | N/A |  | 1.5 |  |  | 1.4 |
Transfer |  | — |  |  | — |  |  | 1.2 |  |  | 1.9 |
Obligation at December 31 |  | $ | 2,352.4 |  |  | $ | 2,315.9 |  |  | $ | 448.1 |  |  | $ | 402.3 |
Change in fair value of plan assets |  |  |  |  |  |  |  |
Fair value at January 1 |  | $ | 2,628.0 |  |  | $ | 3,328.9 |  |  | $ | 835.3 |  |  | $ | 1,000.2 |
Actual return on plan assets |  | 214.9 |  |  | (431.3) |  |  | 76.4 |  |  | (135.4) |
Employer contributions net of plan transfer (1) |  | 14.6 |  |  | 11.4 |  |  | (47.9) |  |  | 3.7 |
Participant contributions |  | — |  |  | — |  |  | 11.8 |  |  | 12.5 |
Benefit payments |  | (191.7) |  |  | (281.0) |  |  | (46.0) |  |  | (45.7) |
Fair value at December 31 |  | $ | 2,665.8 |  |  | $ | 2,628.0 |  |  | $ | 829.6 |  |  | $ | 835.3 |
Funded status at December 31 |  | $ | 313.4 |  |  | $ | 312.1 |  |  | $ | 381.5 |  |  | $ | 433.0 |
(1) Employer contribution includes a $50.0 million transfer out of the WEC Energy Group Retiree Welfare Plan, in 2023, associated with the overfunded position of this plan.
Amounts recognized on the balance sheets at December 31 related to the funded status of the benefit plans | The amounts recognized on our balance sheets at December 31 related to the funded status of the benefit plans were as follows:
|  | Pension Benefits |  | OPEB Benefits
(in millions) |  | 2023 |  | 2022 |  | 2023 |  | 2022
Pension and OPEB assets |  | $ | 475.2 |  |  | $ | 470.6 |  |  | $ | 395.7 |  |  | $ | 446.1 |
Pension and OPEB obligations |  | 161.8 |  |  | 158.5 |  |  | 14.2 |  |  | 13.1 |
Total net assets |  | $ | 313.4 |  |  | $ | 312.1 |  |  | $ | 381.5 |  |  | $ | 433.0 |
Defined Benefit Plan Disclosure [Line Items] |
Amounts that had not yet been recognized in the entity's net periodic benefit cost | The following table shows the amounts that had not yet been recognized in our net periodic benefit cost (credit) as of December 31:
|  | Pension Benefits |  | OPEB Benefits
(in millions) |  | 2023 |  | 2022 |  | 2023 |  | 2022
Pre-tax accumulated other comprehensive income (loss) (1) |  |  |  |  |  |  |  |
Net actuarial loss (gain) |  | $ | 12.7 |  |  | $ | 12.2 |  |  | $ | (1.2) |  |  | $ | (1.6) |
Prior service credits |  | — |  |  | — |  |  | — |  |  | — |
Total |  | $ | 12.7 |  |  | $ | 12.2 |  |  | $ | (1.2) |  |  | $ | (1.6) |
Net regulatory assets (liabilities) (2) |  |  |  |  |  |  |  |
Net actuarial loss (gain) |  | $ | 688.9 |  |  | $ | 669.2 |  |  | $ | (166.3) |  |  | $ | (200.8) |
Prior service credits |  | (2.2) |  |  | (2.1) |  |  | (29.3) |  |  | (44.2) |
Total |  | $ | 686.7 |  |  | $ | 667.1 |  |  | $ | (195.6) |  |  | $ | (245.0) |
(1) Amounts related to the nonregulated entities are included in accumulated other comprehensive loss. (2) Amounts related to the utilities and WBS are recorded as net regulatory assets or liabilities.
Schedule of the components of net periodic benefit cost | The components of net periodic benefit cost (credit) (including amounts capitalized to our balance sheets) for the years ended December 31 were as follows:
|  | Pension Benefits |  | OPEB Benefits
(in millions) |  | 2023 |  | 2022 |  | 2021 |  | 2023 |  | 2022 |  | 2021
Service cost |  | $ | 24.0 |  |  | $ | 50.8 |  |  | $ | 54.3 |  |  | $ | 9.8 |  |  | $ | 14.3 |  |  | $ | 15.7 |
Interest cost |  | 122.3 |  |  | 91.8 |  |  | 87.5 |  |  | 21.6 |  |  | 15.4 |  |  | 14.5 |
Expected return on plan assets |  | (187.4) |  |  | (208.0) |  |  | (200.9) |  |  | (53.0) |  |  | (68.9) |  |  | (66.0) |
Plan settlement |  | 1.3 |  |  | 6.2 |  |  | 3.9 |  |  | — |  |  | — |  |  | — |
Plan curtailment |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (6.4) |
Amortization of prior service cost (credit) |  | — |  |  | 1.6 |  |  | 1.6 |  |  | (14.8) |  |  | (15.9) |  |  | (15.9) |
Amortization of net actuarial loss (gain) |  | 33.0 |  |  | 75.3 |  |  | 109.4 |  |  | (12.3) |  |  | (24.7) |  |  | (24.4) |
Net periodic benefit cost (credit) |  | $ | (6.8) |  |  | $ | 17.7 |  |  | $ | 55.8 |  |  | $ | (48.7) |  |  | $ | (79.8) |  |  | $ | (82.5) |
Weighted-average assumptions used to determine benefit obligations and net periodic benefit cost for the plans | The weighted-average assumptions used to determine the benefit obligations for the plans were as follows for the years ended December 31:
|  | Pension Benefits |  | OPEB Benefits
|  | 2023 |  | 2022 |  | 2023 |  | 2022
Discount rate |  | 5.19% |  | 5.49% |  | 5.16% |  | 5.50%
Rate of compensation increase |  | 4.00% |  | 4.00% |  | N/A |  | N/A
Interest credit rate |  | 4.84% |  | 4.61% |  | N/A |  | N/A
Assumed medical cost trend rate (Pre 65) |  | N/A |  | N/A |  | 6.25% |  | 6.50%
Ultimate trend rate (Pre 65) |  | N/A |  | N/A |  | 5.00% |  | 5.00%
Year ultimate trend rate is reached (Pre 65) |  | N/A |  | N/A |  | 2031 |  | 2031
Assumed medical cost trend rate (Post 65) |  | N/A |  | N/A |  | 6.39% |  | 6.00%
Ultimate trend rate (Post 65) |  | N/A |  | N/A |  | 5.00% |  | 5.00%
Year ultimate trend rate is reached (Post 65) |  | N/A |  | N/A |  | 2030 |  | 2031
The weighted-average assumptions used to determine the net periodic benefit cost for the plans were as follows for the years ended December 31:
|  | Pension Benefits
|  | 2023 |  | 2022 |  | 2021
Discount rate |  | 5.49% |  | 3.18% |  | 2.71%
Expected return on plan assets |  | 6.62% |  | 6.88% |  | 6.88%
Rate of compensation increase |  | 4.00% |  | 4.00% |  | 4.00%
Interest credit rate |  | 4.62% |  | 3.78% |  | 3.71%
|  | OPEB Benefits
|  | 2023 |  | 2022 |  | 2021
Discount rate |  | 5.50% |  | 2.92% |  | 2.66%
Expected return on plan assets |  | 6.50% |  | 7.00% |  | 7.00%
Assumed medical cost trend rate (Pre 65) |  | 6.50% |  | 5.70% |  | 5.85%
Ultimate trend rate (Pre 65) |  | 5.00% |  | 5.00% |  | 5.00%
Year ultimate trend rate is reached (Pre 65) |  | 2031 |  | 2028 |  | 2028
Assumed medical cost trend rate (Post 65) |  | 6.00% |  | 5.67% |  | 5.80%
Ultimate trend rate (Post 65) |  | 5.00% |  | 5.00% |  | 5.00%
Year ultimate trend rate is reached (Post 65) |  | 2031 |  | 2028 |  | 2028
Investments recorded at fair value, by asset class | The following tables provide the fair values of our investments by asset class:
|  | December 31, 2023
|  | Pension Plan Assets |  | OPEB Assets
(in millions) |  | Level 1 |  | Level 2 |  | Level 3 |  | Total |  | Level 1 |  | Level 2 |  | Level 3 |  | Total
Asset Class |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
United States equity |  | $ | 179.3 |  |  | $ | — |  |  | $ | — |  |  | $ | 179.3 |  |  | $ | 91.8 |  |  | $ | — |  |  | $ | — |  |  | $ | 91.8 |
International equity |  | 174.0 |  |  | — |  |  | — |  |  | 174.0 |  |  | 84.6 |  |  | — |  |  | — |  |  | 84.6 |
Fixed income securities: (1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
United States bonds |  | — |  |  | 906.6 |  |  | — |  |  | 906.6 |  |  | 91.5 |  |  | 203.2 |  |  | — |  |  | 294.7 |
International bonds |  | — |  |  | 88.0 |  |  | — |  |  | 88.0 |  |  | — |  |  | 11.9 |  |  | — |  |  | 11.9 |
|  | 353.3 |  |  | 994.6 |  |  | — |  |  | 1,347.9 |  |  | 267.9 |  |  | 215.1 |  |  | — |  |  | 483.0 |
Investments measured at net asset value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  |  |  |  |  |  | 407.4 |  |  |  |  |  |  |  |  | 182.1 |
Fixed income securities |  |  |  |  |  |  |  | 124.2 |  |  |  |  |  |  |  |  | 47.7 |
Other |  |  |  |  |  |  |  | 786.3 |  |  |  |  |  |  |  |  | 116.8 |
Total |  |  |  |  |  |  |  | $ | 2,665.8 |  |  |  |  |  |  |  |  | $ | 829.6 |
(1) This category represents investment grade bonds of United States and foreign issuers denominated in United States dollars from diverse industries.
|  | December 31, 2022
|  | Pension Plan Assets |  | OPEB Assets
(in millions) |  | Level 1 |  | Level 2 |  | Level 3 |  | Total |  | Level 1 |  | Level 2 |  | Level 3 |  | Total
Asset Class |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
United States equity |  | $ | 231.5 |  |  | $ | — |  |  | $ | — |  |  | $ | 231.5 |  |  | $ | 92.5 |  |  | $ | — |  |  | $ | — |  |  | $ | 92.5 |
International equity |  | 202.2 |  |  | — |  |  | — |  |  | 202.2 |  |  | 83.9 |  |  | — |  |  | — |  |  | 83.9 |
Fixed income securities: (1) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
United States bonds |  | — |  |  | 838.7 |  |  | — |  |  | 838.7 |  |  | 129.8 |  |  | 145.3 |  |  | — |  |  | 275.1 |
International bonds |  | — |  |  | 95.0 |  |  | — |  |  | 95.0 |  |  | — |  |  | 13.2 |  |  | — |  |  | 13.2 |
|  | 433.7 |  |  | 933.7 |  |  | — |  |  | 1,367.4 |  |  | 306.2 |  |  | 158.5 |  |  | — |  |  | 464.7 |
Investments measured at net asset value: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity securities |  |  |  |  |  |  |  | 466.0 |  |  |  |  |  |  |  |  | 186.6 |
Fixed income securities |  |  |  |  |  |  |  | 101.0 |  |  |  |  |  |  |  |  | 65.5 |
Other |  |  |  |  |  |  |  | 693.6 |  |  |  |  |  |  |  |  | 118.5 |
Total |  |  |  |  |  |  |  | $ | 2,628.0 |  |  |  |  |  |  |  |  | $ | 835.3 |
(1) This category represents investment grade bonds of United States and foreign issuers denominated in United States dollars from diverse industries.
Schedule of expected future benefit payments | The following table shows the payments, reflecting expected future service, that we expect to make for pension and OPEB over the next 10 years:
(in millions) |  | Pension Benefits |  | OPEB Benefits |
2024 |  | $ | 207.0 |  |  | $ | 34.3 |  |
2025 |  | 199.6 |  |  | 34.4 |  |
2026 |  | 202.2 |  |  | 34.9 |  |
2027 |  | 193.9 |  |  | 35.4 |  |
2028 |  | 188.8 |  |  | 35.5 |  |
2029-2033 |  | 847.4 |  |  | 175.3 |  |
Pension Benefits |
Defined Benefit Plan Disclosure [Line Items] |
Information for pension or OPEB plans with an accumulated benefit obligation in excess of plan assets | The following table shows information for pension plans with an accumulated benefit obligation in excess of plan assets. Amounts presented are as of December 31:
(in millions) |  | 2023 |  | 2022
Accumulated benefit obligation |  | $ | 300.7 |  |  | $ | 185.7 |
Fair value of plan assets |  | 147.3 |  |  | 32.8 |
Information for pension plans with a projected benefit obligation in excess of plan assets | The following table shows information for pension plans with a projected benefit obligation in excess of plan assets. Amounts presented are as of December 31:
(in millions) |  | 2023 |  | 2022
Projected benefit obligation |  | $ | 306.7 |  |  | $ | 191.3 |
Fair value of plan assets |  | 147.3 |  |  | 32.8 |
OPEB Benefits |
Defined Benefit Plan Disclosure [Line Items] |
Information for pension or OPEB plans with an accumulated benefit obligation in excess of plan assets | The following table shows information for OPEB plans with an accumulated benefit obligation in excess of plan assets. Amounts presented are as of December 31:
(in millions) |  | 2023 |  | 2022
Accumulated benefit obligation |  | $ | 21.0 |  |  | $ | 20.6 |
Fair value of plan assets |  | 6.9 |  |  | 7.4 |

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