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Revenue from Contracts with Customers (Details) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 $ 15,561.4 $ 16,195.7 $ 15,424.9
Revenue, Performance Obligation                      
Fixed Performance Obligations $ 1,497.9               1,497.9    
Revenue Textuals                      
Revenue from Related Parties                 0.0 0.0 0.0
Revenues 3,616.0 $ 4,315.0 $ 3,573.6 $ 4,056.8 $ 3,801.1 $ 4,333.1 $ 4,013.2 $ 4,048.3 15,561.4 16,195.7 15,424.9
2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 953.0               953.0    
2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 160.8               160.8    
2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 160.6               160.6    
After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 223.5               223.5    
Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 11,851.9 12,327.8  
Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 5,713.6 5,941.2  
Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 3,308.2 3,435.1  
Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,607.2 2,725.3  
Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 222.9 226.2  
Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 3,444.2 3,435.7  
Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,062.4 1,316.2  
Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 979.4 766.5  
Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 57.3 50.8  
Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,345.1 1,302.2  
Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 316.7 453.0  
Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 15,612.8 16,216.5  
Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (51.4) (20.8)  
Alternative [Member]                      
Revenue Textuals                      
Revenues                 (113.1) (45.8)  
Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 274.9 268.6 229.5
Revenue Textuals                      
Revenues                 61.7 25.0  
AEP Texas Inc. [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,551.6 1,493.0  
Revenue, Performance Obligation                      
Fixed Performance Obligations 387.0               387.0    
Current Assets                      
Affiliated Companies - Contracts with Customers 10.1       15.0       10.1 15.0  
Revenue Textuals                      
Revenue from Related Parties                 160.5 105.2 65.7
Revenues 391.3 489.3 438.0 390.7 402.0 433.4 388.3 371.6 1,709.3 1,595.3 1,538.4
AEP Texas Inc. [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 387.0               387.0    
AEP Texas Inc. [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
AEP Texas Inc. [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
AEP Texas Inc. [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
AEP Texas Inc. [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,142.3 1,151.0  
AEP Texas Inc. [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 571.5 578.9  
AEP Texas Inc. [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 411.5 414.7  
AEP Texas Inc. [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 129.4 128.0  
AEP Texas Inc. [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 29.9 29.4  
AEP Texas Inc. [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 379.2 313.4  
AEP Texas Inc. [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Texas Inc. [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 379.2 313.4  
AEP Texas Inc. [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 30.1 28.6  
AEP Texas Inc. [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 157.7 102.3  
AEP Texas Inc. [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 0.6 (1.3)  
AEP Texas Inc. [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2.9 3.8 2.4
Revenue Textuals                      
Revenues                 157.1 103.6  
AEP Transmission Co [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,042.1 832.0  
Revenue, Performance Obligation                      
Fixed Performance Obligations 1,090.7               1,090.7    
Current Assets                      
Affiliated Companies - Contracts with Customers 66.1       61.0       66.1 61.0  
Revenue Textuals                      
Revenue from Related Parties                 806.7 598.9 568.1
Revenues 251.3 259.7 266.9 243.5 189.9 194.4 200.1 191.7 1,021.4 776.1 706.9
AEP Transmission Co [Member] | Short-term Contract with Customer [Member]                      
Current Assets                      
Affiliated Companies - Contracts with Customers 65.9       58.6       65.9 58.6  
AEP Transmission Co [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 1,090.7               1,090.7    
AEP Transmission Co [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
AEP Transmission Co [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
AEP Transmission Co [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
AEP Transmission Co [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Co [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Co [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Co [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Co [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Co [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,025.5 816.9  
AEP Transmission Co [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Co [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,025.5 816.9  
Revenue Textuals                      
Revenue from Related Parties                 782.0 646.0  
AEP Transmission Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 16.6 15.1  
AEP Transmission Co [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (20.7) (55.9)  
AEP Transmission Co [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (20.7) (55.9)  
AEP Transmission Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.1 0.2 0.8
Revenue Textuals                      
Revenues                 0.0 0.0  
AEP Transmission Co [Member] | Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 214.6 177.0 138.0
Appalachian Power Co [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,911.1 2,993.2  
Revenue, Performance Obligation                      
Fixed Performance Obligations 225.1               225.1    
Current Assets                      
Affiliated Companies - Contracts with Customers 64.3       73.4       64.3 73.4  
Revenue Textuals                      
Revenue from Related Parties                 205.3 181.4 172.0
Revenues 720.6 755.5 655.8 792.8 718.1 762.0 667.0 820.4 2,924.7 2,967.5 2,934.2
Appalachian Power Co [Member] | Short-term Contract with Customer [Member]                      
Current Assets                      
Affiliated Companies - Contracts with Customers 47.3       52.5       47.3 52.5  
Appalachian Power Co [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 158.0               158.0    
Appalachian Power Co [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 32.3               32.3    
Appalachian Power Co [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 23.2               23.2    
Appalachian Power Co [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 11.6               11.6    
Appalachian Power Co [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,494.2 2,604.8  
Appalachian Power Co [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,266.9 1,342.7  
Appalachian Power Co [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 559.9 580.4  
Appalachian Power Co [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 592.2 604.3  
Appalachian Power Co [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 75.2 77.4  
Appalachian Power Co [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 355.1 333.1  
Appalachian Power Co [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 251.5 250.4  
Revenue Textuals                      
Revenue from Related Parties                 129.0 134.0  
Appalachian Power Co [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 103.6 82.7  
Appalachian Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 61.8 55.3  
Appalachian Power Co [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 13.6 (25.7)  
Appalachian Power Co [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 13.6 (23.8)  
Appalachian Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 11.2 9.0 13.2
Revenue Textuals                      
Revenues                 0.0 (1.9)  
Indiana Michigan Power Co [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,308.1 2,381.0  
Revenue, Performance Obligation                      
Fixed Performance Obligations 51.6               51.6    
Current Assets                      
Affiliated Companies - Contracts with Customers 53.7       75.0       53.7 75.0  
Revenue Textuals                      
Revenue from Related Parties                 10.5 22.1 1.8
Revenues 538.2 611.1 543.1 614.3 574.5 629.7 589.7 576.8 2,306.7 2,370.7 2,121.2
Indiana Michigan Power Co [Member] | Short-term Contract with Customer [Member]                      
Current Assets                      
Affiliated Companies - Contracts with Customers 37.1       35.3       37.1 35.3  
Indiana Michigan Power Co [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 29.6               29.6    
Indiana Michigan Power Co [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 8.8               8.8    
Indiana Michigan Power Co [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 8.8               8.8    
Indiana Michigan Power Co [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 4.4               4.4    
Indiana Michigan Power Co [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,782.2 1,787.8  
Indiana Michigan Power Co [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 730.0 730.0  
Indiana Michigan Power Co [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 494.2 485.0  
Indiana Michigan Power Co [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 550.7 565.6  
Indiana Michigan Power Co [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 7.3 7.2  
Indiana Michigan Power Co [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 427.5 493.6  
Indiana Michigan Power Co [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 402.4 470.5  
Indiana Michigan Power Co [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 25.1 23.1  
Indiana Michigan Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 98.4 99.6  
Indiana Michigan Power Co [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (1.4) (10.3)  
Indiana Michigan Power Co [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (1.4) (2.1)  
Indiana Michigan Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 10.7 12.6 14.3
Revenue Textuals                      
Revenue from Related Parties                 73.0 70.0  
Revenues                 0.0 (8.2)  
Ohio Power Co [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,748.8 3,079.9  
Revenue, Performance Obligation                      
Fixed Performance Obligations 61.0               61.0    
Current Assets                      
Affiliated Companies - Contracts with Customers 59.3       70.8       59.3 70.8  
Revenue Textuals                      
Revenue from Related Parties                 27.3 21.0 24.4
Revenues 643.6 710.6 606.6 836.8 745.4 778.3 748.8 790.9 2,797.6 3,063.4 2,883.9
Ohio Power Co [Member] | Short-term Contract with Customer [Member]                      
Current Assets                      
Affiliated Companies - Contracts with Customers 33.9       46.1       33.9 46.1  
Ohio Power Co [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 61.0               61.0    
Ohio Power Co [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Ohio Power Co [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Ohio Power Co [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Ohio Power Co [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,553.5 2,845.3  
Ohio Power Co [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,502.0 1,611.6  
Ohio Power Co [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 738.5 835.6  
Ohio Power Co [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 299.9 385.2  
Ohio Power Co [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 13.1 12.9  
Ohio Power Co [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 56.0 58.5  
Ohio Power Co [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Ohio Power Co [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 56.0 58.5  
Ohio Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 139.3 176.1  
Ohio Power Co [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 48.8 (16.5)  
Ohio Power Co [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 31.7 (20.8)  
Ohio Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 10.8 8.6 6.0
Revenue Textuals                      
Revenues                 17.1 4.3  
Public Service Co Of Oklahoma [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,512.8 1,536.4  
Revenue, Performance Obligation                      
Fixed Performance Obligations 11.7               11.7    
Current Assets                      
Affiliated Companies - Contracts with Customers 20.6       26.2       20.6 26.2  
Revenue Textuals                      
Revenue from Related Parties                 6.1 5.4 4.3
Revenues 307.9 493.0 348.1 332.8 330.8 481.4 398.3 336.8 1,481.8 1,547.3 1,427.2
Public Service Co Of Oklahoma [Member] | Short-term Contract with Customer [Member]                      
Current Assets                      
Affiliated Companies - Contracts with Customers 9.7       12.4       9.7 12.4  
Public Service Co Of Oklahoma [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 11.7               11.7    
Public Service Co Of Oklahoma [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Public Service Co Of Oklahoma [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Public Service Co Of Oklahoma [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Public Service Co Of Oklahoma [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,423.8 1,440.8  
Public Service Co Of Oklahoma [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 650.2 659.0  
Public Service Co Of Oklahoma [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 388.5 394.2  
Public Service Co Of Oklahoma [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 303.5 304.0  
Public Service Co Of Oklahoma [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 81.6 83.6  
Public Service Co Of Oklahoma [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 67.0 76.5  
Public Service Co Of Oklahoma [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 39.5 36.3  
Public Service Co Of Oklahoma [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 27.5 40.2  
Public Service Co Of Oklahoma [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 22.0 19.1  
Public Service Co Of Oklahoma [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (31.0) 10.9  
Public Service Co Of Oklahoma [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (31.0) 10.9  
Public Service Co Of Oklahoma [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 6.1 4.3 5.4
Revenue Textuals                      
Revenues                 0.0 0.0  
Southwestern Electric Power Co [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,799.2 1,817.0  
Revenue, Performance Obligation                      
Fixed Performance Obligations 30.4               30.4    
Current Assets                      
Affiliated Companies - Contracts with Customers 34.5       28.8       34.5 28.8  
Revenue Textuals                      
Revenue from Related Parties                 36.9 35.1 25.9
Revenues 408.8 $ 545.5 $ 375.5 $ 421.1 410.1 $ 535.3 $ 457.1 $ 419.4 1,750.9 1,821.9 1,779.9
Southwestern Electric Power Co [Member] | Short-term Contract with Customer [Member]                      
Current Assets                      
Affiliated Companies - Contracts with Customers 17.6       $ 16.3       17.6 16.3  
Southwestern Electric Power Co [Member] | 2020 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 30.4               30.4    
Southwestern Electric Power Co [Member] | 2021-2022 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Southwestern Electric Power Co [Member] | 2023-2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations 0.0               0.0    
Southwestern Electric Power Co [Member] | After 2024 [Member]                      
Revenue, Performance Obligation                      
Fixed Performance Obligations $ 0.0               0.0    
Southwestern Electric Power Co [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,471.7 1,467.8  
Southwestern Electric Power Co [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 638.6 641.6  
Southwestern Electric Power Co [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 485.4 483.9  
Southwestern Electric Power Co [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 338.7 333.7  
Southwestern Electric Power Co [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 9.0 8.6  
Southwestern Electric Power Co [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 301.4 325.2  
Southwestern Electric Power Co [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 194.7 216.8  
Southwestern Electric Power Co [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 106.7 108.4  
Southwestern Electric Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 26.1 24.0  
Southwestern Electric Power Co [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (48.3) 4.9  
Southwestern Electric Power Co [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (48.3) 4.9  
Southwestern Electric Power Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1.4 1.6 1.9
Revenue Textuals                      
Revenues                 0.0 0.0  
Consolidation Eliminations [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0 0.0
Revenue Textuals                      
Revenue from Related Parties                 (1,314.8) (942.4) (949.0)
Revenues                 (1,314.8) (942.4) (949.0)
Consolidation Eliminations [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (0.9) 0.0  
Consolidation Eliminations [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Consolidation Eliminations [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Consolidation Eliminations [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (0.9) 0.0  
Consolidation Eliminations [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Consolidation Eliminations [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (960.6) (865.1)  
Consolidation Eliminations [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 (7.3)  
Consolidation Eliminations [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (825.0) (737.1)  
Consolidation Eliminations [Member] | Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Consolidation Eliminations [Member] | Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (135.6) (120.7)  
Consolidation Eliminations [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (147.1) (32.0)  
Consolidation Eliminations [Member] | Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 (1,108.6) (897.1)  
Consolidation Eliminations [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (206.2) (45.3)  
Consolidation Eliminations [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (66.9) 52.7  
Consolidation Eliminations [Member] | Other Revenues [Member]                      
Revenue Textuals                      
Revenue from Related Parties                   98.0  
Revenues                 (139.3) (98.0)  
Consolidation Eliminations [Member] | AEP Transmission Co [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0 0.0
Revenue Textuals                      
Revenue from Related Parties                 0.0 0.0 0.0
Revenues                 0.0 0.0 0.0
Consolidation Eliminations [Member] | AEP Transmission Co [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0 0.0
Vertically Integrated Utilities [Member]                      
Revenue Textuals                      
Revenue from Related Parties                 121.4 88.8 96.9
Revenues                 9,367.1 9,645.5 9,192.0
Vertically Integrated Utilities [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 8,157.1 8,331.5  
Vertically Integrated Utilities [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 3,643.7 3,751.8  
Vertically Integrated Utilities [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,155.3 2,183.4  
Vertically Integrated Utilities [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,179.0 2,212.8  
Vertically Integrated Utilities [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 179.1 183.5  
Vertically Integrated Utilities [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,099.7 1,182.0  
Vertically Integrated Utilities [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 807.6 899.8  
Vertically Integrated Utilities [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 292.1 282.2  
Vertically Integrated Utilities [Member] | Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Vertically Integrated Utilities [Member] | Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Vertically Integrated Utilities [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 168.2 158.4  
Vertically Integrated Utilities [Member] | Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 9,425.0 9,671.9  
Vertically Integrated Utilities [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (57.9) (26.4)  
Vertically Integrated Utilities [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (57.9) (15.9)  
Vertically Integrated Utilities [Member] | Other Revenues [Member]                      
Revenue Textuals                      
Revenues                 0.0 (10.5)  
Transmission And Distribution Utilities [Member]                      
Revenue Textuals                      
Revenue from Related Parties                 163.5 100.8 90.4
Revenues                 4,482.5 4,653.1 4,419.3
Transmission And Distribution Utilities [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 3,695.7 3,996.3  
Transmission And Distribution Utilities [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 2,069.9 2,189.4  
Transmission And Distribution Utilities [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,152.9 1,251.7  
Transmission And Distribution Utilities [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 429.1 512.5  
Transmission And Distribution Utilities [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 43.8 42.7  
Transmission And Distribution Utilities [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 435.1 372.1  
Transmission And Distribution Utilities [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Transmission And Distribution Utilities [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 435.1 372.1  
Transmission And Distribution Utilities [Member] | Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Transmission And Distribution Utilities [Member] | Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Transmission And Distribution Utilities [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 169.4 204.6  
Transmission And Distribution Utilities [Member] | Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 4,300.2 4,573.0  
Transmission And Distribution Utilities [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 182.3 80.1  
Transmission And Distribution Utilities [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 32.3 (22.2)  
Transmission And Distribution Utilities [Member] | Other Revenues [Member]                      
Revenue Textuals                      
Revenues                 150.0 102.3  
AEP Transmission Holdco [Member]                      
Revenue Textuals                      
Revenues                 1,073.2 804.1  
AEP Transmission Holdco [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,077.2 849.3  
AEP Transmission Holdco [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,077.2 849.3  
Revenue Textuals                      
Revenue from Related Parties                 794.0 643.0  
AEP Transmission Holdco [Member] | Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
AEP Transmission Holdco [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 16.6 15.2  
AEP Transmission Holdco [Member] | Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,093.8 864.5  
AEP Transmission Holdco [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (20.6) (60.4)  
AEP Transmission Holdco [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 (20.6) (60.4)  
AEP Transmission Holdco [Member] | Other Revenues [Member]                      
Revenue Textuals                      
Revenues                 0.0 0.0  
Generation and Marketing [Member]                      
Revenue Textuals                      
Revenue from Related Parties                 135.8 122.2 103.7
Revenues                 1,857.6 1,940.3 1,875.1
Generation and Marketing [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Generation and Marketing [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Generation and Marketing [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Generation and Marketing [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Generation and Marketing [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Generation and Marketing [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,792.8 1,897.4  
Generation and Marketing [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 254.8 423.7  
Generation and Marketing [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Generation and Marketing [Member] | Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 57.3 50.8  
Generation and Marketing [Member] | Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,480.7 1,422.9  
Revenue Textuals                      
Revenue from Related Parties                 136.0 121.0  
Generation and Marketing [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 4.9 20.6  
Generation and Marketing [Member] | Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 1,797.7 1,918.0  
Generation and Marketing [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 59.9 22.3  
Generation and Marketing [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 0.0 0.0  
Generation and Marketing [Member] | Other Revenues [Member]                      
Revenue Textuals                      
Revenues                 59.9 22.3  
Other Segments [Member]                      
Revenue Textuals                      
Revenue from Related Parties                 81.1 75.1 69.7
Revenues                 95.8 95.1 120.8
Other Segments [Member] | Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Residential [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Commercial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Industrial [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Other Retail [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Wholesale and Competitive [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Wholesale Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Wholesale Transmission [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Renewable Generation [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Retail, Trading and Marketing Revenue [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 0.0 0.0  
Other Segments [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 104.7 86.2  
Other Segments [Member] | Affiliated and Nonaffiliated [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 104.7 86.2  
Other Segments [Member] | Alternative and Other [Member]                      
Revenue Textuals                      
Revenues                 (8.9) 8.9  
Other Segments [Member] | Alternative [Member]                      
Revenue Textuals                      
Revenues                 0.0 0.0  
Other Segments [Member] | Other Revenues [Member]                      
Disaggregation of Revenue                      
Revenue from Contracts with Customers                 14.7 20.0 $ 51.1
Revenue Textuals                      
Revenues                 $ (8.9) $ 8.9