Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	(13.50%)	12.00%	(1.00%)	15.00%
Income Tax Expense (Benefit)	$ 54.4	$ (72.2)	$ 9.9	$ (174.2)
Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (97.0)		$ (164.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(25.40%)		(16.20%)
Kentucky Legislation - House Bill 487 [Member]
Kentucky Single Corporate Tax Rate		5.00%
Kentucky Legislation - House Bill 366 [Member]
Kentucky Net Operating Loss Limitation Percent		80.00%
Remeasurement of Kentucky Deferred Taxes [Member]
Income Tax Expense (Benefit)		$ 18.0
AEP Texas Inc. [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	(234.40%)	16.20%	(84.00%)	16.20%
Income Tax Expense (Benefit)	$ 56.5	$ (9.0)	$ 52.5	$ (18.1)
AEP Texas Inc. [Member] | Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (58.0)		$ (59.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(239.70%)		(95.00%)
AEP Transmission Co [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	19.50%	22.70%	20.10%	21.70%
Income Tax Expense (Benefit)	$ (33.0)	$ (24.1)	$ (60.6)	$ (46.1)
AEP Transmission Co [Member] | FERC PJM 2018 ROE Settlement - AFUDC Adjustment [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (3.0)		$ (3.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(1.70%)		(0.90%)
AEP Transmission Co [Member] | Kentucky Legislation - House Bill 487 [Member]
Kentucky Single Corporate Tax Rate		5.00%
AEP Transmission Co [Member] | Kentucky Legislation - House Bill 366 [Member]
Kentucky Net Operating Loss Limitation Percent		80.00%
Appalachian Power Co [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	(52.10%)	17.00%	(29.50%)	17.80%
Income Tax Expense (Benefit)	$ 19.0	$ (15.8)	$ 43.1	$ (43.8)
Appalachian Power Co [Member] | Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (24.0)		$ (65.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(65.90%)		(44.80%)
Indiana Michigan Power Co [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	(0.20%)	0.70%	(1.80%)	7.60%
Income Tax Expense (Benefit)	$ 0.1	$ (0.7)	$ 2.8	$ (13.1)
Indiana Michigan Power Co [Member] | Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount			$ (8.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent			(5.80%)
Indiana Michigan Power Co [Member] | Flow-Through Items [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (4.0)		$ (9.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(5.40%)		(5.70%)
Indiana Michigan Power Co [Member] | State Income Tax Expenses [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ 2.0		$ 5.0
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	3.20%		3.10%
Indiana Michigan Power Co [Member] | Kentucky Legislation - House Bill 487 [Member]
Kentucky Single Corporate Tax Rate		5.00%
Indiana Michigan Power Co [Member] | Kentucky Legislation - House Bill 366 [Member]
Kentucky Net Operating Loss Limitation Percent		80.00%
Ohio Power Co [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	16.40%	21.60%	14.30%	21.00%
Income Tax Expense (Benefit)	$ (9.9)	$ (19.0)	$ (29.7)	$ (39.5)
Ohio Power Co [Member] | Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (2.0)		$ (11.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(4.00%)		(5.10%)
Ohio Power Co [Member] | Kentucky Legislation - House Bill 487 [Member]
Kentucky Single Corporate Tax Rate		5.00%
Ohio Power Co [Member] | Kentucky Legislation - House Bill 366 [Member]
Kentucky Net Operating Loss Limitation Percent		80.00%
Public Service Co Of Oklahoma [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	0.70%	14.90%	0.60%	14.50%
Income Tax Expense (Benefit)	$ (0.3)	$ (6.4)	$ (0.3)	$ (5.0)
Public Service Co Of Oklahoma [Member] | Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (7.0)		$ (8.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(16.90%)		(16.90%)
Public Service Co Of Oklahoma [Member] | Amortization of Excess ADIT Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ 1.0
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	2.40%		2.70%
Southwestern Electric Power Co [Member]
Federal Statutory Income Tax Rate	21.00%	21.00%	21.00%	21.00%
Effective Income Tax Rate	0.00%	12.40%	2.00%	14.00%
Income Tax Expense (Benefit)	$ 0.0	$ (5.4)	$ (0.7)	$ (8.3)
Southwestern Electric Power Co [Member] | Amortization of Excess ADIT Not Subject to Normalization Requirements [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (1.0)		$ (4.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(8.40%)		(10.80%)
Southwestern Electric Power Co [Member] | State Income Tax Expenses [Member]
Effective Income Tax Rate Reconciliation, Variance Explanation, Amount	$ (1.0)		$ (1.0)
Effective Income Tax Rate Reconciliation, Variance Explanation, Percent	(1.30%)		(1.20%)