Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Sep. 30, 2019
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	2.30%		2.50%
Tax Reform Excess ADIT Reversal	(9.20%)		(9.40%)
Production and Investment Tax Credits	(5.50%)		(4.30%)
Flow Through	0.30%		0.50%
AFUDC Equity	(0.90%)		(1.40%)
Parent Company Loss Benefit	0.00%		0.00%
Discrete Tax Adjustments	0.50%		0.00%
Other	0.10%		(0.40%)
Effective Income Tax Rate	8.60%		8.50%
Income Taxes (Textuals) [Abstract]
Income Taxes Receivable				$ 95
Tax Cuts and Jobs Act, Change in Tax Rate, Deferred Tax Asset, Income Tax Expense		$ 48
AEP Texas Inc. [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	1.40%		1.50%
Tax Reform Excess ADIT Reversal	(7.80%)		(6.20%)
Production and Investment Tax Credits	(0.30%)		(0.40%)
Flow Through	0.30%		0.10%
AFUDC Equity	(1.40%)		(2.60%)
Parent Company Loss Benefit	0.00%		(0.20%)
Discrete Tax Adjustments	0.00%		0.00%
Other	0.10%		0.30%
Effective Income Tax Rate	13.30%		13.50%
AEP Transmission Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	2.70%		2.90%
Tax Reform Excess ADIT Reversal	0.30%		0.40%
Production and Investment Tax Credits	0.00%		0.00%
Flow Through	0.20%		0.50%
AFUDC Equity	(1.70%)		(2.60%)
Parent Company Loss Benefit	(1.90%)		(0.90%)
Discrete Tax Adjustments	0.00%		0.00%
Other	0.10%		0.00%
Effective Income Tax Rate	20.70%		21.30%
Appalachian Power Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	3.20%		3.00%
Tax Reform Excess ADIT Reversal	(18.00%)		(13.00%)
Production and Investment Tax Credits	0.00%		0.00%
Flow Through	1.60%		1.50%
AFUDC Equity	(1.10%)		(1.00%)
Parent Company Loss Benefit	(2.90%)		(3.30%)
Discrete Tax Adjustments	0.00%		0.00%
Other	0.10%		0.10%
Effective Income Tax Rate	3.90%		8.30%
Indiana Michigan Power Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	1.30%		3.20%
Tax Reform Excess ADIT Reversal	(17.90%)		(19.60%)
Production and Investment Tax Credits	(1.70%)		(1.90%)
Flow Through	(1.00%)		0.20%
AFUDC Equity	(0.20%)		(1.10%)
Parent Company Loss Benefit	(2.50%)		(3.90%)
Discrete Tax Adjustments	0.00%		2.70%
Other	0.00%		(0.20%)
Effective Income Tax Rate	(1.00%)		0.40%
Ohio Power Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	0.70%		0.70%
Tax Reform Excess ADIT Reversal	(9.70%)		(10.20%)
Production and Investment Tax Credits	0.00%		0.00%
Flow Through	1.10%		1.00%
AFUDC Equity	(1.10%)		(1.00%)
Parent Company Loss Benefit	0.00%		(0.10%)
Discrete Tax Adjustments	(4.00%)		0.00%
Other	0.20%		0.00%
Effective Income Tax Rate	8.20%		11.40%
Public Service Co Of Oklahoma [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	4.70%		4.60%
Tax Reform Excess ADIT Reversal	(24.70%)		(23.10%)
Production and Investment Tax Credits	(8.20%)		(1.30%)
Flow Through	0.60%		0.60%
AFUDC Equity	(0.50%)		(0.70%)
Parent Company Loss Benefit	0.00%		(2.20%)
Discrete Tax Adjustments	0.00%		0.00%
Other	(0.90%)		0.10%
Effective Income Tax Rate	(8.00%)		(1.00%)
Southwestern Electric Power Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal Statutory Rate	21.00%		21.00%
State Income Tax, net of Federal Benefit	(0.80%)		2.70%
Tax Reform Excess ADIT Reversal	(5.90%)		(94.70%)
Production and Investment Tax Credits	(5.10%)		(0.50%)
Flow Through	(0.70%)		(1.00%)
AFUDC Equity	(0.40%)		(0.40%)
Parent Company Loss Benefit	0.00%		(2.40%)
Discrete Tax Adjustments	0.00%		0.00%
Other	0.10%		7.20%
Effective Income Tax Rate	8.20%		(68.10%)