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Derivatives and Hedging (Details)
gal in Millions, MWh in Millions, MMBTU in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2020
USD ($)
MWh
MMBTU
gal
Mar. 31, 2019
USD ($)
Dec. 31, 2019
USD ($)
MWh
MMBTU
gal
Cash Collateral Netting      
Cash Collateral Received Netted Against Risk Management Assets $ 0   $ 5,000,000
Cash Collateral Paid Netted Against Risk Management Liabilities 76,000,000   39,000,000
Fair Value of Derivative Instruments      
Current Risk Management Assets 130,400,000   172,800,000
Long-term Risk Management Assets 323,700,000   266,600,000
Total Assets 454,100,000   439,400,000
Current Risk Management Liabilities 156,800,000   114,300,000
Long-term Risk Management Liabilities 291,900,000   261,800,000
Total Liabilities 448,700,000   376,100,000
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (32,900,000) $ (24,900,000)  
Carrying Amount of Hedged Asset (Liability) [1] (553,400,000)   (510,800,000)
Cumulative Fair Value Hedging Adjustment in the Carrying Amount of the Hedged Asset (Liability) [1] (57,000,000.0)   (14,500,000)
Gain (Loss) on Hedging Instruments      
Gain (Loss) on Fair Value Hedging Instruments [2] 42,500,000 11,100,000  
Gain (Loss) on Fair Value Portion of Long Term Debt [2] (42,500,000) (11,100,000)  
Collateral Triggering Events [Abstract]      
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions 310,400,000   267,300,000
Amount of Cash Collateral Posted 1,600,000   3,700,000
Additional Settlement Liability if Cross Default Provision is Triggered 282,900,000   246,700,000
AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (1,400,000) 400,000  
Appalachian Power Co [Member]      
Cash Collateral Netting      
Cash Collateral Paid Netted Against Risk Management Liabilities 5,000,000   1,000,000
Fair Value of Derivative Instruments      
Current Risk Management Assets 18,100,000   39,400,000
Long-term Risk Management Assets 100,000   100,000
Total Assets 18,200,000    
Current Risk Management Liabilities 15,000,000.0   1,900,000
Long-term Risk Management Liabilities 100,000   0
Total Liabilities 15,100,000    
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (16,000,000.0) (34,000,000.0)  
Collateral Triggering Events [Abstract]      
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions 2,200,000   2,300,000
Amount of Cash Collateral Posted 0   0
Additional Settlement Liability if Cross Default Provision is Triggered 200,000   400,000
Indiana Michigan Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets 6,700,000   9,800,000
Long-term Risk Management Assets 100,000   100,000
Current Risk Management Liabilities 1,700,000   500,000
Long-term Risk Management Liabilities 100,000   0
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 2,600,000 7,200,000  
Collateral Triggering Events [Abstract]      
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions 1,300,000   1,300,000
Amount of Cash Collateral Posted 0   0
Additional Settlement Liability if Cross Default Provision is Triggered 100,000   200,000
Ohio Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Liabilities 8,700,000   7,300,000
Long-term Risk Management Liabilities 112,200,000   96,300,000
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (15,000,000.0) (9,100,000)  
Public Service Co Of Oklahoma [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets 6,400,000   15,800,000
Current Risk Management Liabilities 100,000   0
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 7,600,000 6,700,000  
Southwestern Electric Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets 2,600,000   6,400,000
Current Risk Management Liabilities 2,200,000   1,900,000
Long-term Risk Management Liabilities 2,900,000   3,100,000
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 1,300,000 4,600,000  
Collateral Triggering Events [Abstract]      
Fair Value Of Derivative Liabilities Subject To Cross Default Provisions 5,500,000   5,100,000
Amount of Cash Collateral Posted 0   0
Additional Settlement Liability if Cross Default Provision is Triggered 5,500,000   5,100,000
Risk Management Contracts [Member]      
Fair Value of Derivative Instruments      
Total Assets [3] 379,100,000 [4]   408,800,000 [5]
Total Liabilities [3] 266,600,000 [4]   239,000,000.0 [5]
Risk Management Contracts [Member] | AEP Texas Inc. [Member]      
Fair Value of Derivative Instruments      
Total Liabilities [3] 0    
Risk Management Contracts [Member] | Appalachian Power Co [Member]      
Fair Value of Derivative Instruments      
Total Assets [3],[6] 17,900,000   39,500,000
Total Liabilities [3],[6] 9,800,000   1,900,000
Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]      
Fair Value of Derivative Instruments      
Total Assets [3],[6] 6,800,000   9,900,000
Total Liabilities [3],[6] 1,800,000   500,000
Risk Management Contracts [Member] | Ohio Power Co [Member]      
Fair Value of Derivative Instruments      
Total Liabilities [3],[6] 120,900,000   103,600,000
Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]      
Fair Value of Derivative Instruments      
Total Assets [3],[6] 6,400,000   15,800,000
Total Liabilities [3],[6] 100,000   0
Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]      
Fair Value of Derivative Instruments      
Total Assets [3],[6] 2,600,000   6,400,000
Total Liabilities [3],[6] 5,100,000   5,000,000.0
Commodity [Member]      
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax (128,500,000)   (103,500,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months $ (73,200,000)   (51,700,000)
Derivatives and Hedging (Textuals) [Abstract]      
Maximum Term for Exposure to Variability of Future Cash Flows 132 months    
Cross Default Provisions Maximum Third Party Obligation Amount $ 50,000,000   50,000,000
Commodity [Member] | Risk Management Contracts [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 412,700,000   513,900,000
Long-term Risk Management Assets [7] 331,600,000   290,800,000
Total Assets [7] 744,300,000   804,700,000
Current Risk Management Liabilities [7] 401,700,000   424,500,000
Long-term Risk Management Liabilities [7] 305,900,000   244,500,000
Total Liabilities [7] 707,600,000   669,000,000.0
Total MTM Derivative Contract Net Assets (Liabilities) [7] 36,700,000   135,700,000
Commodity [Member] | Risk Management Contracts [Member] | AEP Texas Inc. [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 0   0
Long-term Risk Management Assets [7] 0   0
Total Assets [7] 0   0
Current Risk Management Liabilities [7] 1,200,000   0
Long-term Risk Management Liabilities [7] 0   0
Total Liabilities [7] 1,200,000   0
Total MTM Derivative Contract Net Assets (Liabilities) [7] (1,200,000)   0
Commodity [Member] | Risk Management Contracts [Member] | Appalachian Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 71,100,000   124,400,000
Long-term Risk Management Assets [7] 3,500,000   900,000
Total Assets [7] 74,600,000   125,300,000
Current Risk Management Liabilities [7] 68,300,000   86,200,000
Long-term Risk Management Liabilities [7] 3,500,000   700,000
Total Liabilities [7] 71,800,000   86,900,000
Total MTM Derivative Contract Net Assets (Liabilities) [7] 2,800,000   38,400,000
Commodity [Member] | Risk Management Contracts [Member] | Indiana Michigan Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 42,300,000   66,900,000
Long-term Risk Management Assets [7] 2,100,000   500,000
Total Assets [7] 44,400,000   67,400,000
Current Risk Management Liabilities [7] 38,300,000   55,200,000
Long-term Risk Management Liabilities [7] 2,100,000   400,000
Total Liabilities [7] 40,400,000   55,600,000
Total MTM Derivative Contract Net Assets (Liabilities) [7] 4,000,000.0   11,800,000
Commodity [Member] | Risk Management Contracts [Member] | Ohio Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 0   0
Long-term Risk Management Assets [7] 0   0
Total Assets [7] 0   0
Current Risk Management Liabilities [7] 9,600,000   7,300,000
Long-term Risk Management Liabilities [7] 112,200,000   96,300,000
Total Liabilities [7] 121,800,000   103,600,000
Total MTM Derivative Contract Net Assets (Liabilities) [7] (121,800,000)   (103,600,000)
Commodity [Member] | Risk Management Contracts [Member] | Public Service Co Of Oklahoma [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 6,700,000   16,300,000
Long-term Risk Management Assets [7] 0   0
Total Assets [7] 6,700,000   16,300,000
Current Risk Management Liabilities [7] 900,000   500,000
Long-term Risk Management Liabilities [7] 0   0
Total Liabilities [7] 900,000   500,000
Total MTM Derivative Contract Net Assets (Liabilities) [7] 5,800,000   15,800,000
Commodity [Member] | Risk Management Contracts [Member] | Southwestern Electric Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 2,700,000   6,500,000
Long-term Risk Management Assets [7] 0   0
Total Assets [7] 2,700,000   6,500,000
Current Risk Management Liabilities [7] 2,900,000   2,000,000.0
Long-term Risk Management Liabilities [7] 2,900,000   3,100,000
Total Liabilities [7] 5,800,000   5,100,000
Total MTM Derivative Contract Net Assets (Liabilities) [7] (3,100,000)   1,400,000
Commodity [Member] | Hedging Contracts [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 13,500,000   11,500,000
Long-term Risk Management Assets [7] 13,500,000   11,000,000.0
Total Assets [7] 27,000,000.0   22,500,000
Current Risk Management Liabilities [7] 103,200,000   72,300,000
Long-term Risk Management Liabilities [7] 82,900,000   75,700,000
Total Liabilities [7] 186,100,000   148,000,000.0
Total MTM Derivative Contract Net Assets (Liabilities) [7] (159,100,000)   (125,500,000)
Interest Rate [Member]      
Commodity:      
Derivative, Notional Amount 650,000,000.0   625,000,000.0
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax (53,500,000)   (11,500,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months $ (4,300,000)   (2,100,000)
Derivatives and Hedging (Textuals) [Abstract]      
Maximum Term for Exposure to Variability of Future Cash Flows 129 months    
Interest Rate [Member] | AEP Texas Inc. [Member]      
Commodity:      
Derivative, Notional Amount $ 0   0
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax (3,100,000)   (3,400,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months (1,100,000)   (1,100,000)
Interest Rate [Member] | Appalachian Power Co [Member]      
Commodity:      
Derivative, Notional Amount 150,000,000.0   0
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax (3,300,000)   900,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months 1,100,000   900,000
Interest Rate [Member] | Indiana Michigan Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax (9,500,000)   (9,900,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months (1,600,000)   (1,600,000)
Interest Rate [Member] | Ohio Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Interest Rate [Member] | Public Service Co Of Oklahoma [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax 900,000   1,100,000
Portion Expected to be Reclassified to Net Income During the Next Twelve Months 900,000   1,000,000.0
Interest Rate [Member] | Southwestern Electric Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Impact of Cash Flow Hedges on the Condensed Balance Sheet      
AOCI Gain (Loss) Net of Tax (1,400,000)   (1,800,000)
Portion Expected to be Reclassified to Net Income During the Next Twelve Months (1,500,000)   (1,500,000)
Interest Rate [Member] | Hedging Contracts [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 4,600,000   6,500,000
Long-term Risk Management Assets [7] 52,700,000   12,600,000
Total Assets [7] 57,300,000   19,100,000
Current Risk Management Liabilities [7] 5,300,000   0
Long-term Risk Management Liabilities [7] 0   0
Total Liabilities [7] 5,300,000   0
Total MTM Derivative Contract Net Assets (Liabilities) [7] 52,000,000.0   19,100,000
Interest Rate [Member] | Hedging Contracts [Member] | Appalachian Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [7] 300,000    
Long-term Risk Management Assets [7] 0    
Total Assets [7] 300,000    
Current Risk Management Liabilities [7] 5,300,000    
Long-term Risk Management Liabilities [7] 0    
Total Liabilities [7] 5,300,000    
Total MTM Derivative Contract Net Assets (Liabilities) [7] (5,000,000.0)    
Gross Amounts of Risk Management Assets/Liabilities Recognized [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets 430,800,000   531,900,000
Long-term Risk Management Assets 397,800,000   314,400,000
Total Assets 828,600,000   846,300,000
Current Risk Management Liabilities 510,200,000   496,800,000
Long-term Risk Management Liabilities 388,800,000   320,200,000
Total Liabilities 899,000,000.0   817,000,000.0
Total MTM Derivative Contract Net Assets (Liabilities) (70,400,000)   29,300,000
Gross Amounts Offset in the Statement of Financial Position [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] (300,400,000)   (359,100,000)
Long-term Risk Management Assets [8] (74,100,000)   (47,800,000)
Total Assets [8] (374,500,000)   (406,900,000)
Current Risk Management Liabilities [8] (353,400,000)   (382,500,000)
Long-term Risk Management Liabilities [8] (96,900,000)   (58,400,000)
Total Liabilities [8] (450,300,000)   (440,900,000)
Total MTM Derivative Contract Net Assets (Liabilities) [8] 75,800,000   34,000,000.0
Gross Amounts Offset in the Statement of Financial Position [Member] | AEP Texas Inc. [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] 0   0
Long-term Risk Management Assets [8] 0   0
Total Assets [8] 0   0
Current Risk Management Liabilities [8] (1,200,000)   0
Long-term Risk Management Liabilities [8] 0   0
Total Liabilities [8] (1,200,000)   0
Total MTM Derivative Contract Net Assets (Liabilities) [8] 1,200,000   0
Gross Amounts Offset in the Statement of Financial Position [Member] | Appalachian Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] (53,300,000)   (85,000,000.0)
Long-term Risk Management Assets [8] (3,400,000)   (800,000)
Total Assets [8] (56,700,000)   (85,800,000)
Current Risk Management Liabilities [8] (58,600,000)   (84,300,000)
Long-term Risk Management Liabilities [8] (3,400,000)   (700,000)
Total Liabilities [8] (62,000,000.0)   (85,000,000.0)
Total MTM Derivative Contract Net Assets (Liabilities) [8] 5,300,000   (800,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Indiana Michigan Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] (35,600,000)   (57,100,000)
Long-term Risk Management Assets [8] (2,000,000.0)   (400,000)
Total Assets [8] (37,600,000)   (57,500,000)
Current Risk Management Liabilities [8] (36,600,000)   (54,700,000)
Long-term Risk Management Liabilities [8] (2,000,000.0)   (400,000)
Total Liabilities [8] (38,600,000)   (55,100,000)
Total MTM Derivative Contract Net Assets (Liabilities) [8] 1,000,000.0   (2,400,000)
Gross Amounts Offset in the Statement of Financial Position [Member] | Ohio Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] 0   0
Long-term Risk Management Assets [8] 0   0
Total Assets [8] 0   0
Current Risk Management Liabilities [8] (900,000)   0
Long-term Risk Management Liabilities [8] 0   0
Total Liabilities [8] (900,000)   0
Total MTM Derivative Contract Net Assets (Liabilities) [8] 900,000   0
Gross Amounts Offset in the Statement of Financial Position [Member] | Public Service Co Of Oklahoma [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] (300,000)   (500,000)
Long-term Risk Management Assets [8] 0   0
Total Assets [8] (300,000)   (500,000)
Current Risk Management Liabilities [8] (800,000)   (500,000)
Long-term Risk Management Liabilities [8] 0   0
Total Liabilities [8] (800,000)   (500,000)
Total MTM Derivative Contract Net Assets (Liabilities) [8] 500,000   0
Gross Amounts Offset in the Statement of Financial Position [Member] | Southwestern Electric Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [8] (100,000)   (100,000)
Long-term Risk Management Assets [8] 0   0
Total Assets [8] (100,000)   (100,000)
Current Risk Management Liabilities [8] (700,000)   (100,000)
Long-term Risk Management Liabilities [8] 0   0
Total Liabilities [8] (700,000)   (100,000)
Total MTM Derivative Contract Net Assets (Liabilities) [8] 600,000   0
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 130,400,000   172,800,000
Long-term Risk Management Assets [9] 323,700,000   266,600,000
Total Assets [9] 454,100,000   439,400,000
Current Risk Management Liabilities [9] 156,800,000   114,300,000
Long-term Risk Management Liabilities [9] 291,900,000   261,800,000
Total Liabilities [9] 448,700,000   376,100,000
Total MTM Derivative Contract Net Assets (Liabilities) [9] 5,400,000   63,300,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | AEP Texas Inc. [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 0   0
Long-term Risk Management Assets [9] 0   0
Total Assets [9] 0   0
Current Risk Management Liabilities [9] 0   0
Long-term Risk Management Liabilities [9] 0   0
Total Liabilities [9] 0   0
Total MTM Derivative Contract Net Assets (Liabilities) [9] 0   0
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Appalachian Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 18,100,000   39,400,000
Long-term Risk Management Assets [9] 100,000   100,000
Total Assets [9] 18,200,000   39,500,000
Current Risk Management Liabilities [9] 15,000,000.0   1,900,000
Long-term Risk Management Liabilities [9] 100,000   0
Total Liabilities [9] 15,100,000   1,900,000
Total MTM Derivative Contract Net Assets (Liabilities) [9] 3,100,000   37,600,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Indiana Michigan Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 6,700,000   9,800,000
Long-term Risk Management Assets [9] 100,000   100,000
Total Assets [9] 6,800,000   9,900,000
Current Risk Management Liabilities [9] 1,700,000   500,000
Long-term Risk Management Liabilities [9] 100,000   0
Total Liabilities [9] 1,800,000   500,000
Total MTM Derivative Contract Net Assets (Liabilities) [9] 5,000,000.0   9,400,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Ohio Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 0   0
Long-term Risk Management Assets [9] 0   0
Total Assets [9] 0   0
Current Risk Management Liabilities [9] 8,700,000   7,300,000
Long-term Risk Management Liabilities [9] 112,200,000   96,300,000
Total Liabilities [9] 120,900,000   103,600,000
Total MTM Derivative Contract Net Assets (Liabilities) [9] (120,900,000)   (103,600,000)
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Public Service Co Of Oklahoma [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 6,400,000   15,800,000
Long-term Risk Management Assets [9] 0   0
Total Assets [9] 6,400,000   15,800,000
Current Risk Management Liabilities [9] 100,000   0
Long-term Risk Management Liabilities [9] 0   0
Total Liabilities [9] 100,000   0
Total MTM Derivative Contract Net Assets (Liabilities) [9] 6,300,000   15,800,000
Net Amounts of Assets/Liabilities Presented in the Statement of Financial Position [Member] | Southwestern Electric Power Co [Member]      
Fair Value of Derivative Instruments      
Current Risk Management Assets [9] 2,600,000   6,400,000
Long-term Risk Management Assets [9] 0   0
Total Assets [9] 2,600,000   6,400,000
Current Risk Management Liabilities [9] 2,200,000   1,900,000
Long-term Risk Management Liabilities [9] 2,900,000   3,100,000
Total Liabilities [9] 5,100,000   5,000,000.0
Total MTM Derivative Contract Net Assets (Liabilities) [9] $ (2,500,000)   $ 1,400,000
Power [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 305.4   365.9
Power [Member] | AEP Texas Inc. [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 0.0   0.0
Power [Member] | Appalachian Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 38.7   61.0
Power [Member] | Indiana Michigan Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 18.5   26.8
Power [Member] | Ohio Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 3.2   7.1
Power [Member] | Public Service Co Of Oklahoma [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 5.9   14.9
Power [Member] | Southwestern Electric Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MWh 1.7   4.4
Natural Gas [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 42.3   40.7
Natural Gas [Member] | AEP Texas Inc. [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 0.0   0.0
Natural Gas [Member] | Appalachian Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 0.0   0.0
Natural Gas [Member] | Indiana Michigan Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 0.0   0.0
Natural Gas [Member] | Ohio Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 0.0   0.0
Natural Gas [Member] | Public Service Co Of Oklahoma [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 0.0   0.0
Natural Gas [Member] | Southwestern Electric Power Co [Member]      
Commodity:      
Derivative, Energy Notional Amount | MMBTU 10.7   11.6
Heating Oil and Gasoline [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 5.0   6.9
Heating Oil and Gasoline [Member] | AEP Texas Inc. [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 1.3   1.8
Heating Oil and Gasoline [Member] | Appalachian Power Co [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 0.8   1.1
Heating Oil and Gasoline [Member] | Indiana Michigan Power Co [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 0.5   0.6
Heating Oil and Gasoline [Member] | Ohio Power Co [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 1.0   1.4
Heating Oil and Gasoline [Member] | Public Service Co Of Oklahoma [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 0.5   0.7
Heating Oil and Gasoline [Member] | Southwestern Electric Power Co [Member]      
Commodity:      
Derivative, Volume Notional Amount | gal 0.7   0.9
Interest Rate Contract [Member]      
Commodity:      
Derivative, Notional Amount $ 137,100,000   $ 140,100,000
Interest Rate Contract [Member] | AEP Texas Inc. [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Interest Rate Contract [Member] | Appalachian Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Interest Rate Contract [Member] | Indiana Michigan Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Interest Rate Contract [Member] | Ohio Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Interest Rate Contract [Member] | Public Service Co Of Oklahoma [Member]      
Commodity:      
Derivative, Notional Amount 0   0
Interest Rate Contract [Member] | Southwestern Electric Power Co [Member]      
Commodity:      
Derivative, Notional Amount 0   $ 0
Vertically Integrated Utilities Revenues [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 400,000 300,000  
Vertically Integrated Utilities Revenues [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Vertically Integrated Utilities Revenues [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Vertically Integrated Utilities Revenues [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Vertically Integrated Utilities Revenues [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Vertically Integrated Utilities Revenues [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Vertically Integrated Utilities Revenues [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Generation and Marketing Revenues [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (10,300,000) 2,700,000  
Generation and Marketing Revenues [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Generation and Marketing Revenues [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Generation and Marketing Revenues [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Generation and Marketing Revenues [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Generation and Marketing Revenues [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Generation and Marketing Revenues [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Electric Generation, Transmission and Distribution Revenues [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Electric Generation, Transmission and Distribution Revenues [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Electric Generation, Transmission and Distribution Revenues [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 200,000 (100,000)  
Electric Generation, Transmission and Distribution Revenues [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 100,000 300,000  
Electric Generation, Transmission and Distribution Revenues [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Electric Generation, Transmission and Distribution Revenues [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Electric Generation, Transmission and Distribution Revenues [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 100,000  
Purchased Electricity for Resale [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 100,000 1,400,000  
Purchased Electricity for Resale [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Purchased Electricity for Resale [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 100,000 0  
Purchased Electricity for Resale [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Purchased Electricity for Resale [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Purchased Electricity for Resale [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Purchased Electricity for Resale [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Other Operation Expense [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (200,000) (400,000)  
Other Operation Expense [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (100,000) (100,000)  
Other Operation Expense [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 (100,000)  
Other Operation Expense [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Other Operation Expense [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (100,000) (100,000)  
Other Operation Expense [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Other Operation Expense [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Maintenance Expense [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (200,000) (500,000)  
Maintenance Expense [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (100,000) (100,000)  
Maintenance Expense [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts (100,000) 0  
Maintenance Expense [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Maintenance Expense [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 (100,000)  
Maintenance Expense [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 0  
Maintenance Expense [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts 0 (100,000)  
Regulatory Assets [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (33,900,000) (6,400,000)  
Regulatory Assets [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (1,200,000) 600,000  
Regulatory Assets [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (8,900,000) (2,100,000)  
Regulatory Assets [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (700,000) 300,000  
Regulatory Assets [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (18,400,000) (8,900,000)  
Regulatory Assets [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (500,000) 500,000  
Regulatory Assets [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (2,000,000.0) (100,000)  
Regulatory Liabilities [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] 11,200,000 (22,000,000.0)  
Regulatory Liabilities [Member] | AEP Texas Inc. [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] 0 0  
Regulatory Liabilities [Member] | Appalachian Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] (7,300,000) (31,700,000)  
Regulatory Liabilities [Member] | Indiana Michigan Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] 3,200,000 6,600,000  
Regulatory Liabilities [Member] | Ohio Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] 3,500,000 0  
Regulatory Liabilities [Member] | Public Service Co Of Oklahoma [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] 8,100,000 6,200,000  
Regulatory Liabilities [Member] | Southwestern Electric Power Co [Member]      
Amount of Gain (Loss) Recognized on Risk Management Contracts      
Amount of Gain (Loss) Recognized on Risk Management Contracts [10] $ 3,300,000 $ 4,700,000  
[1]
Amounts included on the balance sheets within Long-term Debt Due within One Year and Long-term Debt, respectively.
[2]
Gain (Loss) is included in Interest Expense on the statements of income.
[3]
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.’’
[4]
The March 31, 2020 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 1 matures $(1) million in periods 2021-2023; Level 2 matures $(30) million in 2020, $(9) million in periods 2021-2023 and $(1) million in periods 2024-2025; Level 3 matures $37 million in 2020, $36 million in periods 2021-2023, $25 million in periods 2024-2025 and $(20) million in periods 2026-2032.  Risk management commodity contracts are substantially comprised of power contracts.
[5]
The December 31, 2019 maturity of the net fair value of risk management contracts prior to cash collateral, assets/(liabilities), is as follows: Level 2 matures $(7) million in 2020 and $(3) million in periods 2021-2023; Level 3 matures $96 million in 2020, $36 million in periods 2021-2023, $25 million in periods 2024-2025 and $(12) million in periods 2026-2032.  Risk management commodity contracts are substantially comprised of power contracts.
[6]
Substantially comprised of power contracts for the Registrant Subsidiaries.
[7]
Derivative instruments within these categories are reported gross.  These instruments are subject to master netting agreements and are presented on the balance sheets on a net basis in accordance with the accounting guidance for “Derivatives and Hedging.”
[8]
Amounts include counterparty netting of risk management and hedging contracts and associated cash collateral in accordance with the accounting guidance for “Derivatives and Hedging.”
[9]
All derivative contracts subject to a master netting arrangement or similar agreement are offset in the statement of financial position.
[10]
Represents realized and unrealized gains and losses subject to regulatory accounting treatment recorded as either current or noncurrent on the balance sheets.