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PENSION PLANS AND POST-RETIREMENT BENEFITS PENSION PLANS AND POST-RETIREMENT BENEFITS - Schedule of Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | $ (0.6) | $ 47.0 | $ 3.0
Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 78.9 | 79.1 | 60.7
Interest cost | 96.8 | 108.0 | 82.5
Expected return on plan assets | (105.6) | (106.3) | (86.4)
Prior service cost | 1.8 | 1.9 | 0.7
Recognized net actuarial (gain) loss | 46.4 | 33.0 | 32.6
Settlement and special termination benefits | 11.2 | 15.6 |
Net periodic benefit costs before regulatory adjustment and intercompany allocations | 129.5 | 131.3 | 90.1
Regulatory adjustment | 29.6 | 37.4 | 8.3
Net periodic benefit costs (income) | 159.1 | 168.7 | 98.4
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 112.8 | 34.2 | 47.3
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability | 271.9 | 202.9 | 145.7
Post-Retirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 2.7 | 2.5 | 2.3
Interest cost | 9.2 | 10.5 | 8.0
Expected return on plan assets | (9.3) | (10.0) | (8.8)
Prior service cost | 0.5 | 0.5 | 0.5
Recognized net actuarial (gain) loss | 0.2 | (1.2) | (0.6)
Settlement and special termination benefits | 0.0 | 0.0 |
Net periodic benefit costs before regulatory adjustment and intercompany allocations | 3.3 | 2.3 | 1.4
Regulatory adjustment | (4.0) | (3.4) | (1.7)
Net periodic benefit costs (income) | (0.7) | (1.1) | (0.3)
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 8.4 | 1.6 | 5.0
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability | 7.7 | 0.5 | 4.7
Evergy Kansas Central | Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 27.1 | 29.0 | 32.2
Interest cost | 47.0 | 53.7 | 50.7
Expected return on plan assets | (53.1) | (54.8) | (55.9)
Prior service cost | 1.6 | 1.7 | 0.7
Recognized net actuarial (gain) loss | 33.9 | 25.5 | 32.6
Settlement and special termination benefits | 0.0 | 0.0 |
Net periodic benefit costs before regulatory adjustment and intercompany allocations | 56.5 | 55.1 | 60.3
Regulatory adjustment | 5.9 | 3.0 | 8.8
Intercompany allocations | (0.2) | 0.0 | 0.0
Net periodic benefit costs (income) | 62.2 | 58.1 | 69.1
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 53.1 | 17.4 | (35.1)
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability | 115.3 | 75.5 | 34.0
Evergy Kansas Central | Post-Retirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 1.1 | 1.1 | 1.3
Interest cost | 4.8 | 5.6 | 5.0
Expected return on plan assets | (6.6) | (6.7) | (7.0)
Prior service cost | 0.5 | 0.5 | 0.5
Recognized net actuarial (gain) loss | 0.0 | (0.6) | (0.6)
Settlement and special termination benefits | 0.0 | 0.0 |
Net periodic benefit costs before regulatory adjustment and intercompany allocations | (0.2) | (0.1) | (0.8)
Regulatory adjustment | (3.0) | (3.0) | (2.0)
Intercompany allocations | 0.1 | 0.0 | 0.0
Net periodic benefit costs (income) | (3.1) | (3.1) | (2.8)
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 3.9 | (3.7) | 11.8
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability | 0.8 | (6.8) | 9.0
Evergy Metro |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 0.2 | (0.7) | (3.7)
Evergy Metro | Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 51.8 | 50.1 | 48.6
Interest cost | 49.1 | 53.3 | 49.9
Expected return on plan assets | (54.7) | (48.9) | (55.5)
Prior service cost | 0.8 | 0.9 | 0.7
Recognized net actuarial (gain) loss | 45.7 | 49.8 | 45.1
Settlement and special termination benefits | 14.3 | 23.0 |
Net periodic benefit costs before regulatory adjustment and intercompany allocations | 107.0 | 128.2 | 88.8
Regulatory adjustment | (11.6) | (19.2) | 0.7
Intercompany allocations | (22.6) | (34.4) | (21.6)
Net periodic benefit costs (income) | 72.8 | 74.6 | 67.9
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 24.6 | (37.8) | (17.9)
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability | 97.4 | 36.8 | 50.0
Evergy Metro | Post-Retirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 1.6 | 1.4 | 2.0
Interest cost | 4.4 | 4.9 | 4.8
Expected return on plan assets | (2.7) | (3.3) | (2.8)
Prior service cost | 0.0 | 0.0 | 0.1
Recognized net actuarial (gain) loss | (0.6) | (1.4) | (0.2)
Settlement and special termination benefits | 0.0 | 0.0 |
Net periodic benefit costs before regulatory adjustment and intercompany allocations | 2.7 | 1.6 | 3.9
Regulatory adjustment | (0.2) | 0.4 | (0.1)
Intercompany allocations | (0.3) | (0.4) | (1.1)
Net periodic benefit costs (income) | 2.2 | 1.6 | 2.7
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Total recognized in OCI or regulatory asset/liability | 5.3 | 6.1 | (13.9)
Total recognized in net periodic benefit costs and OCI or regulatory asset/liability | 7.5 | 7.7 | (11.2)
Actuarial (gain) loss | Pension Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 169.7 | 84.7 | 67.2
Amounts reclassified from accumulated other comprehensive loss | (59.2) | (48.6) | (32.6)
Actuarial (gain) loss | Post-Retirement Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 8.2 | 0.9 | 4.9
Amounts reclassified from accumulated other comprehensive loss | (0.2) | 1.2 | 0.6
Actuarial (gain) loss | Evergy Kansas Central | Pension Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 80.4 | 44.6 | (13.2)
Amounts reclassified from accumulated other comprehensive loss | (33.8) | (25.5) | (32.6)
Actuarial (gain) loss | Evergy Kansas Central | Post-Retirement Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 3.9 | (3.8) | 11.7
Amounts reclassified from accumulated other comprehensive loss | 0.0 | 0.6 | 0.6
Actuarial (gain) loss | Evergy Metro | Pension Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 89.3 | 35.9 | 25.9
Amounts reclassified from accumulated other comprehensive loss | (60.0) | (72.8) | (45.1)
Actuarial (gain) loss | Evergy Metro | Post-Retirement Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 4.3 | 4.7 | (14.0)
Amounts reclassified from accumulated other comprehensive loss | 0.6 | 1.4 | 0.2
Prior service cost | Pension Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | (4.1) |  | 13.4
Amounts reclassified from accumulated other comprehensive loss | (1.8) | (1.9) | (0.7)
Prior service cost | Post-Retirement Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | (0.9) |  | 0.0
Amounts reclassified from accumulated other comprehensive loss | (0.5) | (0.5) | (0.5)
Prior service cost | Evergy Kansas Central | Pension Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | (8.1) |  | 11.4
Amounts reclassified from accumulated other comprehensive loss | (1.6) | (1.7) | (0.7)
Prior service cost | Evergy Kansas Central | Post-Retirement Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | (0.5) |  | 0.0
Amounts reclassified from accumulated other comprehensive loss | (0.5) | (0.5) | (0.5)
Prior service cost | Evergy Metro | Pension Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | 3.9 |  | 2.0
Amounts reclassified from accumulated other comprehensive loss | (0.8) | (0.9) | (0.7)
Prior service cost | Evergy Metro | Post-Retirement Benefits |  |  |
Other changes in plan assets and benefit obligations recognized in OCI or regulatory assets/liabilities |  |  |
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax | (0.4) |  | 0.0
Amounts reclassified from accumulated other comprehensive loss | $ 0.0 | $ 0.0 | $ (0.1)

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