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Fair Value Financial Assets Liabilities (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Derivative Assets |  | $ 538,700,000 |  | $ 632,900,000 |  |
Derivative Liabilities |  | 471,400,000 |  | 490,400,000 |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 263,200,000 |  | 234,700,000 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 3,860,200,000 |  | 3,341,200,000 |  |
Total Assets |  | 4,662,100,000 |  | 4,208,800,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 538,700,000 |  | 632,900,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 471,400,000 |  | 490,400,000 |  |
Changes in the Fair Value of Net Trading Derivatives and Other Investments |  |  |  |  |  |
Beginning Balance |  | 160,400,000 |  | 103,100,000 |  | $ 113,300,000
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) | [1],[2] | 52,100,000 |  | 69,500,000 |  | 48,600,000
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date | [2] | 71,100,000 |  | (34,900,000) |  | (45,200,000)
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income | [3] | (17,400,000) |  | 9,600,000 |  | 24,200,000
Settlements |  | (172,200,000) |  | (154,600,000) |  | (89,000,000.0)
Transfers into Level 3 | [4],[5] | (6,100,000) |  | 1,700,000 |  | (3,800,000)
Transfers out of Level 3 | [5] | 3,800,000 |  | 100,000 |  | (34,400,000)
Changes in Fair Value Allocated to Regulated Jurisdiction | [6] | 47,700,000 |  | 165,900,000 |  | 89,400,000
Ending Balance |  | 139,400,000 |  | 160,400,000 |  | 103,100,000
Other [Member] |  |  |  |  |  |
Derivative Assets |  | (625,500,000) |  | (1,264,300,000) |  |
Derivative Liabilities |  | (608,800,000) |  | (784,700,000) |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 13,900,000 |  | 9,000,000.0 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 9,000,000.0 |  | 9,900,000 |  |
Total Assets |  | (602,600,000) |  | (1,245,400,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | (625,500,000) |  | (1,264,300,000) |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | (608,800,000) |  | (784,700,000) |  |
Level 1 [Member] |  |  |  |  |  |
Derivative Assets |  | 9,700,000 |  | 15,000,000.0 |  |
Derivative Liabilities |  | 24,700,000 |  | 21,800,000 |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 249,300,000 |  | 225,700,000 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 2,444,400,000 |  | 2,142,600,000 |  |
Total Assets |  | 2,703,400,000 |  | 2,383,300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 9,700,000 |  | 15,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 24,700,000 |  | 21,800,000 |  |
Level 2 [Member] |  |  |  |  |  |
Derivative Assets |  | 860,400,000 |  | 1,541,100,000 |  |
Derivative Liabilities |  | 900,800,000 |  | 1,072,600,000 |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,406,800,000 |  | 1,188,700,000 |  |
Total Assets |  | 2,267,200,000 |  | 2,729,800,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 860,400,000 |  | 1,541,100,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 900,800,000 |  | 1,072,600,000 |  |
Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 294,100,000 |  | 341,100,000 |  |
Derivative Liabilities |  | 154,700,000 |  | 180,700,000 |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Total Assets |  | 294,100,000 |  | 341,100,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 294,100,000 |  | 341,100,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 154,700,000 |  | 180,700,000 |  |
2023 [Member] | Level 1 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | (7,000,000) |  |
2023 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 182,000,000 |  |
2023 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 128,000,000 |  |
2024 [Member] | Level 1 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | (11,000,000) |  |  |  |
2024 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | (99,000,000) |  |  |  |
2024 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | 74,000,000 |  |  |  |
2024 - 2026 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 134,000,000 |  |
2024 - 2026 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 6,000,000 |  |
2025 - 2027 [Member] | Level 1 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | (4,000,000) |  |  |  |
2025 - 2027 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | (44,000,000) |  |  |  |
2025 - 2027 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | 43,000,000 |  |  |  |
2027 - 2028 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 10,000,000 |  |
2027 - 2028 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 6,000,000 |  |
2028-2029 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | 7,000,000 |  |  |  |
2028-2029 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | 18,000,000 |  |  |  |
2029 - 2033 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | 1,000,000 |  |
2029 - 2033 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  |  |  | (5,000,000) |  |
2030 - 2033 [Member] | Level 2 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | 2,000,000 |  |  |  |
2030 - 2033 [Member] | Level 3 [Member] |  |  |  |  |  |
Fair Value Measurements 1 (Textuals) |  |  |  |  |  |
Maturity Of Net Fair Value Of Risk Management Contracts Prior to Cash Collateral, Assets/Liabilities |  | (16,000,000) |  |  |  |
Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Assets | [8] | 403,900,000 | [7] | 315,400,000 | [9] |
Derivative Liabilities | [8] | 362,300,000 | [7] | 339,800,000 | [9] |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 403,900,000 | [7] | 315,400,000 | [9] |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 362,300,000 | [7] | 339,800,000 | [9] |
Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets | [8] | (617,000,000.0) | [7] | (1,211,500,000) | [9] |
Derivative Liabilities | [8] | (600,300,000) | [7] | (731,900,000) | [9] |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | (617,000,000.0) | [7] | (1,211,500,000) | [9] |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (600,300,000) | [7] | (731,900,000) | [9] |
Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 9,700,000 | [7] | 15,000,000.0 | [9] |
Derivative Liabilities | [8] | 24,700,000 | [7] | 21,800,000 | [9] |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 9,700,000 | [7] | 15,000,000.0 | [9] |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 24,700,000 | [7] | 21,800,000 | [9] |
Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 736,900,000 | [7] | 1,197,500,000 | [9] |
Derivative Liabilities | [8] | 783,800,000 | [7] | 870,900,000 | [9] |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 736,900,000 | [7] | 1,197,500,000 | [9] |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 783,800,000 | [7] | 870,900,000 | [9] |
Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 274,300,000 | [7] | 314,400,000 | [9] |
Derivative Liabilities | [8] | 154,100,000 | [7] | 179,000,000.0 | [9] |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 274,300,000 | [7] | 314,400,000 | [9] |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 154,100,000 | [7] | 179,000,000.0 | [9] |
Energy Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 225,500,000 |  | 204,000,000.0 |  |
Derivative Liabilities |  | 144,900,000 |  | 167,400,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 225,500,000 |  | 204,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 144,900,000 |  | 167,400,000 |  |
Energy Contracts [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 5.21 |  | 2.91 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 5.21 |  | 2.91 |  |
Energy Contracts [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 153.77 |  | 187.34 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 153.77 |  | 187.34 |  |
Energy Contracts [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 45.05 |  | 49.14 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 45.05 |  | 49.14 |  |
Natural Gas Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 0 |  |  |  |
Derivative Liabilities |  | 500,000 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 500,000 |  |  |  |
Natural Gas Contracts [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Natural Gas Contracts [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Natural Gas Contracts [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [11],[12] | 3.11 |  |  |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [11],[12] | 3.11 |  |  |  |
FTRs [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 68,600,000 |  | 137,100,000 |  |
Derivative Liabilities |  | 9,300,000 |  | 13,300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 68,600,000 |  | 137,100,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 9,300,000 |  | 13,300,000 |  |
FTRs [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (25.45) |  | (36.45) |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (25.45) |  | (36.45) |  |
FTRs [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 17.07 |  | 20.72 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 17.07 |  | 20.72 |  |
FTRs [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 0 |  | 1.18 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 0 |  | 1.18 |  |
Commodity Hedges [Member] |  |  |  |  |  |
Derivative Assets | [8] | 134,800,000 |  | 306,500,000 |  |
Derivative Liabilities | [8] | 1,700,000 |  | 23,200,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 134,800,000 |  | 306,500,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 1,700,000 |  | 23,200,000 |  |
Commodity Hedges [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets | [8] | (8,500,000) |  | (52,800,000) |  |
Derivative Liabilities | [8] | (8,500,000) |  | (52,800,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | (8,500,000) |  | (52,800,000) |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (8,500,000) |  | (52,800,000) |  |
Commodity Hedges [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Commodity Hedges [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 123,500,000 |  | 332,600,000 |  |
Derivative Liabilities | [8] | 9,600,000 |  | 74,300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 123,500,000 |  | 332,600,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 9,600,000 |  | 74,300,000 |  |
Commodity Hedges [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 19,800,000 |  | 26,700,000 |  |
Derivative Liabilities | [8] | 600,000 |  | 1,700,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 19,800,000 |  | 26,700,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 600,000 |  | 1,700,000 |  |
Fair Value Hedges [Member] |  |  |  |  |  |
Derivative Liabilities |  | 98,400,000 |  | 127,400,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 98,400,000 |  | 127,400,000 |  |
Fair Value Hedges [Member] | Other [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  | 0 |  |
Fair Value Hedges [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  | 0 |  |
Fair Value Hedges [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 98,400,000 |  | 127,400,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 98,400,000 |  | 127,400,000 |  |
Fair Value Hedges [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  | 0 |  |
Interest Rate Foreign Currency Hedges [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 11,000,000.0 |  |
Derivative Liabilities |  | 9,000,000.0 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 11,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 9,000,000.0 |  |  |  |
Interest Rate Foreign Currency Hedges [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Derivative Liabilities |  | 0 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Interest Rate Foreign Currency Hedges [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Derivative Liabilities |  | 0 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Interest Rate Foreign Currency Hedges [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 11,000,000.0 |  |
Derivative Liabilities |  | 9,000,000.0 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 11,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 9,000,000.0 |  |  |  |
Interest Rate Foreign Currency Hedges [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Derivative Liabilities |  | 0 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
AEP Texas Inc. [Member] |  |  |  |  |  |
Derivative Liabilities |  | 2,700,000 |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 34,000,000.0 |  | 32,700,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 2,700,000 |  |  |  |
AEP Texas Inc. [Member] | Other [Member] |  |  |  |  |  |
Derivative Liabilities |  | (200,000) |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | (200,000) |  |  |  |
AEP Texas Inc. [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 34,000,000.0 |  | 32,700,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
AEP Texas Inc. [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 2,900,000 |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 2,900,000 |  |  |  |
AEP Texas Inc. [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  |  |  |
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | (200,000) |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (200,000) |  |  |  |
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  |  |  |
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 200,000 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 200,000 |  |  |  |
AEP Texas Inc. [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  |  |  |
AEP Texas Inc. [Member] | Interest Rate Foreign Currency Hedges [Member] |  |  |  |  |  |
Derivative Liabilities |  | 2,700,000 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 2,700,000 |  |  |  |
AEP Texas Inc. [Member] | Interest Rate Foreign Currency Hedges [Member] | Other [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
AEP Texas Inc. [Member] | Interest Rate Foreign Currency Hedges [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
AEP Texas Inc. [Member] | Interest Rate Foreign Currency Hedges [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 2,700,000 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 2,700,000 |  |  |  |
AEP Texas Inc. [Member] | Interest Rate Foreign Currency Hedges [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 0 |  |  |  |
Appalachian Power Co [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 14,900,000 |  | 14,400,000 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  | 37,300,000 |  | 83,500,000 |  |
Changes in the Fair Value of Net Trading Derivatives and Other Investments |  |  |  |  |  |
Beginning Balance |  | 69,100,000 |  | 41,700,000 |  | 19,300,000
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) | [1],[2] | (11,700,000) |  | 3,000,000.0 |  | 8,300,000
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date | [2] | 0 |  | 0 |  | 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income | [3] | 0 |  | 0 |  | 0
Settlements |  | (57,300,000) |  | (44,700,000) |  | (28,000,000.0)
Transfers into Level 3 | [4],[5] | 0 |  | 0 |  | 0
Transfers out of Level 3 | [5] | 0 |  | 0 |  | 0
Changes in Fair Value Allocated to Regulated Jurisdiction | [6] | 22,300,000 |  | 69,100,000 |  | 42,100,000
Ending Balance |  | 22,400,000 |  | 69,100,000 |  | 41,700,000
Appalachian Power Co [Member] | Other [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  | (2,200,000) |  | (1,000,000.0) |  |
Appalachian Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 14,900,000 |  | 14,400,000 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  | 14,900,000 |  | 14,400,000 |  |
Appalachian Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  | 1,100,000 |  | 700,000 |  |
Appalachian Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  | 23,500,000 |  | 69,400,000 |  |
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Assets | [8] | 22,400,000 |  | 69,100,000 |  |
Derivative Liabilities | [8] | 22,500,000 |  | 3,500,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 22,400,000 |  | 69,100,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 22,500,000 |  | 3,500,000 |  |
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets | [8] | (2,200,000) |  | (1,000,000.0) |  |
Derivative Liabilities | [8] | (2,600,000) |  | (1,400,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | (2,200,000) |  | (1,000,000.0) |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (2,600,000) |  | (1,400,000) |  |
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 1,100,000 |  | 700,000 |  |
Derivative Liabilities | [8] | 24,000,000.0 |  | 4,600,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 1,100,000 |  | 700,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 24,000,000.0 |  | 4,600,000 |  |
Appalachian Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 23,500,000 |  | 69,400,000 |  |
Derivative Liabilities | [8] | 1,100,000 |  | 300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 23,500,000 |  | 69,400,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 1,100,000 |  | 300,000 |  |
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 23,500,000 |  | 69,400,000 |  |
Derivative Liabilities |  | 1,100,000 |  | 300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 23,500,000 |  | 69,400,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 1,100,000 |  | 300,000 |  |
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (1.04) |  | (2.82) |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (1.04) |  | (2.82) |  |
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 6.45 |  | 18.88 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 6.45 |  | 18.88 |  |
Appalachian Power Co [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 1.36 |  | 3.89 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 1.36 |  | 3.89 |  |
Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 3,860,200,000 |  | 3,341,200,000 |  |
Total Assets |  | 3,899,800,000 |  | 3,356,600,000 |  |
Changes in the Fair Value of Net Trading Derivatives and Other Investments |  |  |  |  |  |
Beginning Balance |  | 4,600,000 |  | (700,000) |  | 2,100,000
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) | [1],[2] | 4,200,000 |  | 3,700,000 |  | (100,000)
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date | [2] | 0 |  | 0 |  | 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income | [3] | 0 |  | 0 |  | 0
Settlements |  | (8,800,000) |  | (3,000,000.0) |  | (2,200,000)
Transfers into Level 3 | [4],[5] | 0 |  | 0 |  | 0
Transfers out of Level 3 | [5] | 0 |  | 0 |  | 0
Changes in Fair Value Allocated to Regulated Jurisdiction | [6] | 2,800,000 |  | 4,600,000 |  | (500,000)
Ending Balance |  | 2,800,000 |  | 4,600,000 |  | (700,000)
Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 9,000,000.0 |  | 9,900,000 |  |
Total Assets |  | 6,700,000 |  | 8,700,000 |  |
Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 2,444,400,000 |  | 2,142,600,000 |  |
Total Assets |  | 2,444,400,000 |  | 2,142,600,000 |  |
Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,406,800,000 |  | 1,188,700,000 |  |
Total Assets |  | 1,444,200,000 |  | 1,200,000,000 |  |
Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Total Assets |  | 4,500,000 |  | 5,300,000 |  |
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Assets | [8] | 39,600,000 |  | 15,400,000 |  |
Derivative Liabilities | [8] | 2,000,000.0 |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 39,600,000 |  | 15,400,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 2,000,000.0 |  | 0 |  |
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets | [8] | (2,300,000) |  | (1,200,000) |  |
Derivative Liabilities | [8] | (3,400,000) |  | (1,300,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | (2,300,000) |  | (1,200,000) |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (3,400,000) |  | (1,300,000) |  |
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 37,400,000 |  | 11,300,000 |  |
Derivative Liabilities | [8] | 3,700,000 |  | 600,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 37,400,000 |  | 11,300,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 3,700,000 |  | 600,000 |  |
Indiana Michigan Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 4,500,000 |  | 5,300,000 |  |
Derivative Liabilities | [8] | 1,700,000 |  | 700,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 4,500,000 |  | 5,300,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 1,700,000 |  | 700,000 |  |
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 4,500,000 |  | 5,300,000 |  |
Derivative Liabilities |  | 1,700,000 |  | 700,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 4,500,000 |  | 5,300,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 1,700,000 |  | 700,000 |  |
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (1.48) |  | 0.16 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (1.48) |  | 0.16 |  |
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 8.40 |  | 18.79 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 8.40 |  | 18.79 |  |
Indiana Michigan Power Co [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 0.85 |  | 1.23 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 0.85 |  | 1.23 |  |
Ohio Power Co [Member] |  |  |  |  |  |
Changes in the Fair Value of Net Trading Derivatives and Other Investments |  |  |  |  |  |
Beginning Balance |  | (40,000,000.0) |  | (92,500,000) |  | (110,300,000)
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) | [1],[2] | (3,600,000) |  | 6,500,000 |  | 2,400,000
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date | [2] | 0 |  | 0 |  | 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income | [3] | 0 |  | 0 |  | 0
Settlements |  | 5,600,000 |  | 300,000 |  | 6,300,000
Transfers into Level 3 | [4],[5] | 0 |  | 0 |  | 0
Transfers out of Level 3 | [5] | 0 |  | 0 |  | 0
Changes in Fair Value Allocated to Regulated Jurisdiction | [6] | (12,600,000) |  | 45,700,000 |  | 9,100,000
Ending Balance |  | (50,600,000) |  | (40,000,000.0) |  | (92,500,000)
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 50,700,000 |  | 39,700,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 50,700,000 |  | 39,700,000 |  |
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | (100,000) |  | (300,000) |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (100,000) |  | (300,000) |  |
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 200,000 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 200,000 |  | 0 |  |
Ohio Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Liabilities | [8] | 50,600,000 |  | 40,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 50,600,000 |  | 40,000,000.0 |  |
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 0 |  | 0 |  |
Derivative Liabilities |  | 50,600,000 |  | 40,000,000.0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 50,600,000 |  | 40,000,000.0 |  |
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 22.92 |  | 2.91 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 22.92 |  | 2.91 |  |
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 67.53 |  | 187.34 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 67.53 |  | 187.34 |  |
Ohio Power Co [Member] | Energy Contracts [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 42.85 |  | 48.76 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | 42.85 |  | 48.76 |  |
Public Service Co Of Oklahoma [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  |  |  | 25,300,000 |  |
Changes in the Fair Value of Net Trading Derivatives and Other Investments |  |  |  |  |  |
Beginning Balance |  | 23,700,000 |  | 12,100,000 |  | 10,300,000
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) | [1],[2] | 29,800,000 |  | 24,200,000 |  | 16,100,000
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date | [2] | 0 |  | 0 |  | 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income | [3] | 0 |  | 0 |  | 0
Settlements |  | (53,400,000) |  | (36,300,000) |  | (26,400,000)
Transfers into Level 3 | [4],[5] | 0 |  | 0 |  | 0
Transfers out of Level 3 | [5] | 0 |  | 0 |  | 0
Changes in Fair Value Allocated to Regulated Jurisdiction | [6] | 18,500,000 |  | 23,700,000 |  | 12,100,000
Ending Balance |  | 18,600,000 |  | 23,700,000 |  | 12,100,000
Public Service Co Of Oklahoma [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  |  |  | (300,000) |  |
Public Service Co Of Oklahoma [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  |  |  | 0 |  |
Public Service Co Of Oklahoma [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  |  |  | 1,600,000 |  |
Public Service Co Of Oklahoma [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Total Assets |  |  |  | 24,000,000.0 |  |
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Assets | [8] | 19,000,000.0 |  | 25,300,000 |  |
Derivative Liabilities | [8] | 29,900,000 |  | 1,600,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 19,000,000.0 |  | 25,300,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 29,900,000 |  | 1,600,000 |  |
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets | [8] | (700,000) |  | 1,300,000 |  |
Derivative Liabilities | [8] | (800,000) |  | (400,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | (700,000) |  | 1,300,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (800,000) |  | (400,000) |  |
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Derivative Liabilities | [8] | 29,600,000 |  | 1,700,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 29,600,000 |  | 1,700,000 |  |
Public Service Co Of Oklahoma [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 19,700,000 |  | 24,000,000.0 |  |
Derivative Liabilities | [8] | 1,100,000 |  | 300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 19,700,000 |  | 24,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 1,100,000 |  | 300,000 |  |
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 19,700,000 |  | 24,000,000.0 |  |
Derivative Liabilities |  | 1,100,000 |  | 300,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 19,700,000 |  | 24,000,000.0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 1,100,000 |  | 300,000 |  |
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (25.45) |  | (36.45) |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (25.45) |  | (36.45) |  |
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 4.80 |  | 3.40 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 4.80 |  | 3.40 |  |
Public Service Co Of Oklahoma [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | (4.33) |  | (7.55) |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | (4.33) |  | (7.55) |  |
Public Service Co Of Oklahoma [Member] | Interest Rate Foreign Currency Hedges [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Public Service Co Of Oklahoma [Member] | Interest Rate Foreign Currency Hedges [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | (1,600,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | (1,600,000) |  |
Public Service Co Of Oklahoma [Member] | Interest Rate Foreign Currency Hedges [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Public Service Co Of Oklahoma [Member] | Interest Rate Foreign Currency Hedges [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 1,600,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 1,600,000 |  |
Public Service Co Of Oklahoma [Member] | Interest Rate Foreign Currency Hedges [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  |  |  | 0 |  |
Southwestern Electric Power Co [Member] |  |  |  |  |  |
Changes in the Fair Value of Net Trading Derivatives and Other Investments |  |  |  |  |  |
Beginning Balance |  | 14,200,000 |  | 10,900,000 |  | 1,600,000
Realized Gain (Loss) Included in Net Income (or Changes in Net Assets) | [1],[2] | 20,000,000.0 |  | 35,800,000 |  | 9,500,000
Unrealized Gain (Loss) Included in Net Income (or Changes in Net Assets) Relating to Assets Still Held at the Reporting Date | [2] | 0 |  | 0 |  | 0
Realized and Unrealized Gains (Losses) Included in Other Comprehensive Income | [3] | 0 |  | 0 |  | 0
Settlements |  | (34,200,000) |  | (45,000,000.0) |  | (15,500,000)
Transfers into Level 3 | [4],[5] | 0 |  | 0 |  | 0
Transfers out of Level 3 | [5] | 0 |  | 6,900,000 |  | 0
Changes in Fair Value Allocated to Regulated Jurisdiction | [6] | 11,100,000 |  | 5,600,000 |  | 15,300,000
Ending Balance |  | 11,100,000 |  | 14,200,000 |  | $ 10,900,000
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] |  |  |  |  |  |
Derivative Assets | [8] | 11,600,000 |  | 16,400,000 |  |
Derivative Liabilities | [8] | 15,600,000 |  | 1,400,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 11,600,000 |  | 16,400,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 15,600,000 |  | 1,400,000 |  |
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Other [Member] |  |  |  |  |  |
Derivative Assets | [8] | (900,000) |  | (400,000) |  |
Derivative Liabilities | [8] | (1,000,000.0) |  | (600,000) |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | (900,000) |  | (400,000) |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | (1,000,000.0) |  | (600,000) |  |
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 1 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 0 |  | 0 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 0 |  | 0 |  |
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 2 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 500,000 |  | 2,200,000 |  |
Derivative Liabilities | [8] | 15,700,000 |  | 1,600,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 500,000 |  | 2,200,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 15,700,000 |  | 1,600,000 |  |
Southwestern Electric Power Co [Member] | Risk Management Commodity Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets | [8] | 12,000,000.0 |  | 14,600,000 |  |
Derivative Liabilities | [8] | 900,000 |  | 400,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets | [8] | 12,000,000.0 |  | 14,600,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities | [8] | 900,000 |  | 400,000 |  |
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 0 |  |  |  |
Derivative Liabilities |  | 500,000 |  |  |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 0 |  |  |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 500,000 |  |  |  |
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [12] | 3.11 |  |  |  |
Southwestern Electric Power Co [Member] | Natural Gas Contracts [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [11],[12] | 3.11 |  |  |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [11],[12] | 3.11 |  |  |  |
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] |  |  |  |  |  |
Derivative Assets |  | 12,000,000.0 |  | 14,600,000 |  |
Derivative Liabilities |  | 400,000 |  | 400,000 |  |
Risk Management Assets |  |  |  |  |  |
Derivative Assets |  | 12,000,000.0 |  | 14,600,000 |  |
Liabilities, Fair Value Disclosure |  |  |  |  |  |
Derivative Liabilities |  | 400,000 |  | 400,000 |  |
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] | Low [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (25.45) |  | (36.45) |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | (25.45) |  | (36.45) |  |
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] | High [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 4.80 |  | 3.40 |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10] | 4.80 |  | 3.40 |  |
Southwestern Electric Power Co [Member] | FTRs [Member] | Level 3 [Member] | Weighted Average [Member] |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | (4.33) |  | (7.55) |  |
Level 3 Quantitative Information |  |  |  |  |  |
Fair Value Significant Unobservable Input Price Per Unit | [10],[11] | (4.33) |  | (7.55) |  |
Cash [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 48,900,000 |  | 47,100,000 |  |
Other Temporary Investments | [13] | 48,900,000 |  | 47,100,000 |  |
Cash [Member] | Other [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Cash [Member] | Level 1 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 48,900,000 |  | 47,100,000 |  |
Cash [Member] | Level 2 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Cash [Member] | Level 3 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Cash and Cash Equivalents |  | 0 |  | 0 |  |
Other Cash Deposits [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 13,900,000 |  | 9,000,000.0 |  |
Other Cash Deposits [Member] | Other [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [14] | 13,900,000 |  | 9,000,000.0 |  |
Other Cash Deposits [Member] | Level 1 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Other Cash Deposits [Member] | Level 2 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Other Cash Deposits [Member] | Level 3 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Mutual Funds Fixed Income [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [15] | 159,700,000 |  | 144,100,000 |  |
Mutual Funds Fixed Income [Member] | Other [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Mutual Funds Fixed Income [Member] | Level 1 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 159,700,000 |  | 144,100,000 |  |
Mutual Funds Fixed Income [Member] | Level 2 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Mutual Funds Fixed Income [Member] | Level 3 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments |  | 0 |  | 0 |  |
Mutual Funds Equity [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [16] | 40,700,000 |  | 34,500,000 |  |
Mutual Funds Equity [Member] | Other [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [16] | 0 |  | 0 |  |
Mutual Funds Equity [Member] | Level 1 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [16] | 40,700,000 |  | 34,500,000 |  |
Mutual Funds Equity [Member] | Level 2 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [16] | 0 |  | 0 |  |
Mutual Funds Equity [Member] | Level 3 [Member] |  |  |  |  |  |
Assets, Fair Value Disclosure |  |  |  |  |  |
Other Temporary Investments | [16] | 0 |  | 0 |  |
Cash and Cash Equivalents [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 16,800,000 |  | 21,200,000 |  |
Cash and Cash Equivalents [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 9,000,000.0 |  | 9,900,000 |  |
Cash and Cash Equivalents [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 7,800,000 |  | 11,300,000 |  |
Cash and Cash Equivalents [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 0 |  | 0 |  |
Cash and Cash Equivalents [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 0 |  | 0 |  |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 16,800,000 |  | 21,200,000 |  |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 9,000,000.0 |  | 9,900,000 |  |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 7,800,000 |  | 11,300,000 |  |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 0 |  | 0 |  |
Cash and Cash Equivalents [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [17] | 0 |  | 0 |  |
US Government Agencies Debt Securities [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,273,000,000 |  | 1,123,800,000 |  |
US Government Agencies Debt Securities [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
US Government Agencies Debt Securities [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
US Government Agencies Debt Securities [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,273,000,000 |  | 1,123,800,000 |  |
US Government Agencies Debt Securities [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,273,000,000 |  | 1,123,800,000 |  |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,273,000,000 |  | 1,123,800,000 |  |
US Government Agencies Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Corporate Debt Securities [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 132,100,000 |  | 61,600,000 |  |
Corporate Debt Securities [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Corporate Debt Securities [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Corporate Debt Securities [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 132,100,000 |  | 61,600,000 |  |
Corporate Debt Securities [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Corporate Debt Securities [Member] | Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 132,100,000 |  | 61,600,000 |  |
Corporate Debt Securities [Member] | Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Corporate Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Corporate Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 132,100,000 |  | 61,600,000 |  |
Corporate Debt Securities [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
State and Local Jurisdiction |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,700,000 |  | 3,300,000 |  |
State and Local Jurisdiction | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
State and Local Jurisdiction | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
State and Local Jurisdiction | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,700,000 |  | 3,300,000 |  |
State and Local Jurisdiction | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,700,000 |  | 3,300,000 |  |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,700,000 |  | 3,300,000 |  |
State and Local Jurisdiction | Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Fixed Income Funds [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,406,800,000 |  | 1,188,700,000 |  |
Fixed Income Funds [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Fixed Income Funds [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Fixed Income Funds [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,406,800,000 |  | 1,188,700,000 |  |
Fixed Income Funds [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,406,800,000 |  | 1,188,700,000 |  |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 1,406,800,000 |  | 1,188,700,000 |  |
Fixed Income Funds [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  | 0 |  | 0 |  |
Domestic [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 2,436,600,000 |  | 2,131,300,000 |  |
Domestic [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 0 |  | 0 |  |
Domestic [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 2,436,600,000 |  | 2,131,300,000 |  |
Domestic [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 0 |  | 0 |  |
Domestic [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 0 |  | 0 |  |
Domestic [Member] | Indiana Michigan Power Co [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 2,436,600,000 |  | 2,131,300,000 |  |
Domestic [Member] | Indiana Michigan Power Co [Member] | Other [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 0 |  | 0 |  |
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 1 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 2,436,600,000 |  | 2,131,300,000 |  |
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 2 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | 0 |  | 0 |  |
Domestic [Member] | Indiana Michigan Power Co [Member] | Level 3 [Member] |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts |  |  |  |  |  |
Spent Nuclear Fuel and Decommissioning Trusts | [16] | $ 0 |  | $ 0 |  |
[1] | Represents the change in fair value between the beginning of the reporting period and the settlement of the risk management commodity contract.
[2] | Included in revenues on the statements of income.
[3] | Included in cash flow hedges on the statements of comprehensive income.
[4] | Represents existing assets or liabilities that were previously categorized as Level 2.
[5] | Transfers are recognized based on their value at the beginning of the reporting period that the transfer occurred.
[6] | Relates to the net gains (losses) of those contracts that are not reflected on the statements of income. These changes in fair value are recorded as regulatory liabilities for net gains and as regulatory assets for net losses or accounts payable
[7] | The December 31, 2023 maturities of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), were as follows: Level 1 matures $(11) million in 2024 and $(4) million in 2025-2027; Level 2 matures $(99) million in 2024, $(44) million in periods 2025-2027, $7 million in periods 2028-2029 and $2 million in periods 2030-2033; Level 3 matures $74 million in 2024, $43 million in periods 2025-2027, $18 million in periods 2028-2029 and $(16) million in periods 2030-2033. Risk management commodity contracts are substantially comprised of power contracts.
[8] | Amounts in “Other” column primarily represent counterparty netting of risk management and hedging contracts and associated cash collateral under the accounting guidance for “Derivatives and Hedging.”
[9] | The December 31, 2022 maturities of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), were as follows: Level 1 matures $(7) million in 2023; Level 2 matures $182 million in 2023, $134 million in periods 2024-2026; $10 million in periods 2027-2028 and $1 million in periods 2029-2033; Level 3 matures $128 million in 2023, $6 million in periods 2024-2026, $6 million in periods 2027-2028 and $(5) million in periods 2029-2033. Risk management commodity contracts are substantially comprised of power contracts.
[10] | Represents market prices in dollars per MWh.
[11] | The weighted-average is the product of the forward market price of the underlying commodity and volume weighted by term.
[12] | Represents market prices in dollars per MMBtu.
[13] | Primarily represents amounts held for the repayment of debt.
[14] | Amounts in “Other” column primarily represent cash deposits in bank accounts with financial institutions or third-parties. Level 1 and Level 2 amounts primarily represent investments in money market funds.
[15] | Primarily short and intermediate maturities which may be sold and do not contain maturity dates.
[16] | Amounts represent publicly-traded equity securities and equity-based mutual funds.
[17] | Amounts in “Other” column primarily represent accrued interest receivables from financial institutions. Level 1 amounts primarily represent investments in money market funds.

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