Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities
Net Income (Loss)	$ 578.8	$ 499.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	696.3	672.2
Rockport Plant, Unit 2 Operating Lease Amortization	32.8	34.1
Deferred Income Taxes	44.3	27.9
Allowance for Equity Funds Used During Construction	(33.4)	(31.4)
Mark-to-Market of Risk Management Contracts	21.0	57.4
Amortization of Nuclear Fuel	22.7	23.4
Property Taxes	(74.8)	(59.8)
Deferred Fuel Over/Under-Recovery, Net	(1,225.1)	63.1
Change in Other Noncurrent Assets	(168.9)	(84.9)
Change in Other Noncurrent Liabilities	83.5	(74.8)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(12.9)	(32.6)
Fuel, Materials and Supplies	39.5	(35.8)
Accounts Payable	171.8	(111.1)
Accrued Taxes, Net	(80.8)	(93.9)
Other Current Assets	(26.3)	5.3
Other Current Liabilities	(185.7)	(242.7)
Net Cash Flows from (Used for) Operating Activities	(117.2)	615.7
Investing Activities
Construction Expenditures	(1,492.7)	(1,792.7)
Purchases of Investment Securities	(337.6)	(632.7)
Sales of Investment Securities	325.5	635.6
Acquisitions of Nuclear Fuel	(55.9)	(1.3)
Acquisitions of Assets	(102.9)	0.0
Other Investing Activities	29.4	25.1
Net Cash Flows from (Used for) Investing Activities	(1,634.2)	(1,766.0)
Financing Activities
Issuance of Common Stock	184.6	56.1
Issuance of Long-term Debt	1,951.5	1,418.9
Issuance of Short-term Debt with Original Maturities greater than 90 Days	644.2	1,297.5
Change in Short-term Debt with Original Maturities less than 90 Days, Net	16.9	328.3
Retirement of Long-term Debt	(650.7)	(300.5)
Redemption of Short-term Debt with Original Maturities Greater than 90 Days	(92.0)	0.0
Principal Payments for Finance Leases Obligations	(15.0)	(15.4)
Dividends Paid on Common Stock	(372.0)	(363.7)
Other Financing Activities	(30.4)	(32.7)
Net Cash Flows from (Used for) Financing Activities	1,637.1	2,388.5
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(114.3)	1,238.2
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	438.3	432.6
Cash and Cash Equivalents at Beginning of Period	392.7
Cash, Cash Equivalents and Restricted Cash at End of Period	324.0	1,670.8
Cash and Cash Equivalents at End of Period	273.2
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	220.5	212.6
Net Cash Paid (Received) for Income Taxes	(0.2)	(0.6)
Noncash Acquisitions Under Finance Leases	9.0	19.4
Construction Expenditures Included in Current Liabilities as of March 31,	762.7	874.1
Construction Expenditures Included in Noncurrent Liabilities as of March 31,	0.0	8.3
Acquisition of Nuclear Fuel Included in Current Liabilities as of March 31,	6.7	0.0
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	0.1	1.3
AEP Texas Inc. [Member]
Operating Activities
Net Income (Loss)	46.1	47.6
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	97.5	162.5
Deferred Income Taxes	1.7	(7.6)
Allowance for Equity Funds Used During Construction	(4.1)	(5.1)
Property Taxes	(71.1)	(69.3)
Change in Other Noncurrent Assets	(14.8)	(10.8)
Change in Other Noncurrent Liabilities	14.7	3.2
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(6.8)	(34.3)
Fuel, Materials and Supplies	0.3	(7.6)
Accounts Payable	1.4	2.4
Accrued Taxes, Net	34.1	38.9
Other Current Assets	0.3	(1.4)
Other Current Liabilities	(15.2)	(4.6)
Net Cash Flows from (Used for) Operating Activities	84.1	113.9
Investing Activities
Construction Expenditures	(295.1)	(327.5)
Change in Advances to Affiliates, Net	0.3	200.1
Other Investing Activities	17.0	7.4
Net Cash Flows from (Used for) Investing Activities	(277.8)	(120.0)
Financing Activities
Change in Advances from Affiliates, Net	216.9	63.9
Retirement of Long-term Debt	(11.2)	(114.3)
Principal Payments for Finance Leases Obligations	(1.7)	(1.5)
Other Financing Activities	0.3	0.4
Net Cash Flows from (Used for) Financing Activities	204.3	(51.5)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	10.6	(57.6)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	28.8	157.8
Cash and Cash Equivalents at Beginning of Period	0.1
Cash, Cash Equivalents and Restricted Cash at End of Period	39.4	100.2
Cash and Cash Equivalents at End of Period	0.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	30.0	21.1
Noncash Acquisitions Under Finance Leases	0.8	3.7
Construction Expenditures Included in Current Liabilities as of March 31,	120.5	175.1
AEP Transmission Co [Member]
Operating Activities
Net Income (Loss)	151.7	117.8
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	70.6	56.0
Deferred Income Taxes	8.3	13.7
Allowance for Equity Funds Used During Construction	(16.7)	(16.2)
Property Taxes	30.0	28.4
Change in Other Noncurrent Assets	1.4	2.4
Change in Other Noncurrent Liabilities	0.6	0.6
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(16.5)	(22.0)
Fuel, Materials and Supplies	(0.3)	0.4
Accounts Payable	(18.9)	22.7
Accrued Taxes, Net	(35.1)	(37.8)
Accrued Interest	24.3	19.4
Other Current Assets	0.9	0.4
Other Current Liabilities	1.4	1.2
Net Cash Flows from (Used for) Operating Activities	201.7	187.0
Investing Activities
Construction Expenditures	(400.5)	(491.5)
Change in Advances to Affiliates, Net	3.0	(43.0)
Other Investing Activities	(0.8)	2.1
Net Cash Flows from (Used for) Investing Activities	(398.3)	(532.4)
Financing Activities
Capital Contributions from Parent	124.0	185.0
Change in Advances from Affiliates, Net	72.6	160.4
Net Cash Flows from (Used for) Financing Activities	196.6	345.4
Net Increase (Decrease) in Cash and Cash Equivalents	0.0	0.0
Cash and Cash Equivalents at Beginning of Period	0.0	0.0
Cash and Cash Equivalents at End of Period	0.0	0.0
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	8.9	9.3
Net Cash Paid (Received) for Income Taxes	0.0	0.1
Construction Expenditures Included in Current Liabilities as of March 31,	244.5	290.6
Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	122.5	115.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	135.8	122.2
Deferred Income Taxes	(1.7)	(5.1)
Allowance for Equity Funds Used During Construction	(3.5)	(2.4)
Mark-to-Market of Risk Management Contracts	12.1	29.6
Deferred Fuel Over/Under-Recovery, Net	(6.4)	7.6
Change in Other Noncurrent Assets	(54.3)	(24.4)
Change in Other Noncurrent Liabilities	6.8	(16.1)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	25.1	(2.6)
Fuel, Materials and Supplies	25.2	(5.5)
Accounts Payable	46.0	(86.6)
Accrued Taxes, Net	8.2	14.5
Other Current Assets	(3.6)	19.2
Other Current Liabilities	3.1	(11.1)
Net Cash Flows from (Used for) Operating Activities	315.3	154.6
Investing Activities
Construction Expenditures	(187.5)	(219.1)
Change in Advances to Affiliates, Net	(239.7)	0.3
Other Investing Activities	6.6	1.1
Net Cash Flows from (Used for) Investing Activities	(420.6)	(217.7)
Financing Activities
Issuance of Long-term Debt	494.3	0.0
Change in Advances from Affiliates, Net	(18.6)	118.6
Retirement of Long-term Debt	(362.5)	(12.2)
Principal Payments for Finance Leases Obligations	(1.9)	(1.8)
Dividends Paid on Common Stock	(12.5)	(50.0)
Other Financing Activities	0.2	0.2
Net Cash Flows from (Used for) Financing Activities	99.0	54.8
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(6.3)	(8.3)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	22.7	26.8
Cash and Cash Equivalents at Beginning of Period	5.8
Cash, Cash Equivalents and Restricted Cash at End of Period	16.4	18.5
Cash and Cash Equivalents at End of Period	4.8
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	28.9	31.9
Noncash Acquisitions Under Finance Leases	0.4	1.9
Construction Expenditures Included in Current Liabilities as of March 31,	96.1	103.7
Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	70.8	92.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	109.2	93.9
Rockport Plant, Unit 2 Operating Lease Amortization	16.6	17.3
Deferred Income Taxes	(12.1)	(16.3)
Amortization (Deferral) of Incremental Nuclear Refueling Outage Expenses, Net	4.9	15.2
Allowance for Equity Funds Used During Construction	(3.5)	(2.0)
Mark-to-Market of Risk Management Contracts	2.7	4.4
Amortization of Nuclear Fuel	22.7	23.4
Deferred Fuel Over/Under-Recovery, Net	(9.3)	22.5
Change in Other Noncurrent Assets	2.6	(2.9)
Change in Other Noncurrent Liabilities	24.1	10.0
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	14.4	8.6
Fuel, Materials and Supplies	8.8	(16.2)
Accounts Payable	(14.8)	(21.6)
Accrued Taxes, Net	21.6	25.0
Other Current Assets	5.2	18.2
Other Current Liabilities	(45.8)	(62.7)
Net Cash Flows from (Used for) Operating Activities	218.1	209.1
Investing Activities
Construction Expenditures	(120.2)	(141.4)
Change in Advances to Affiliates, Net	0.0	(0.1)
Purchases of Investment Securities	(336.9)	(626.0)
Sales of Investment Securities	320.0	612.4
Acquisitions of Nuclear Fuel	(55.9)	(1.3)
Other Investing Activities	3.2	4.2
Net Cash Flows from (Used for) Investing Activities	(189.8)	(152.2)
Financing Activities
Change in Advances from Affiliates, Net	21.6	(10.7)
Retirement of Long-term Debt	(24.1)	(23.7)
Principal Payments for Finance Leases Obligations	(1.5)	(1.5)
Dividends Paid on Common Stock	(25.0)	(21.3)
Other Financing Activities	0.2	0.1
Net Cash Flows from (Used for) Financing Activities	(28.8)	(57.1)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.5)	(0.2)
Cash and Cash Equivalents at Beginning of Period	3.3	2.0
Cash and Cash Equivalents at End of Period	2.8	1.8
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	42.0	44.3
Noncash Acquisitions Under Finance Leases	2.4	1.4
Construction Expenditures Included in Current Liabilities as of March 31,	50.5	67.8
Acquisition of Nuclear Fuel Included in Current Liabilities as of March 31,	6.7	0.0
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	0.1	1.3
Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	68.2	75.1
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	75.1	70.5
Deferred Income Taxes	4.5	12.9
Carrying Costs Income	(0.5)	(0.4)
Allowance for Equity Funds Used During Construction	(2.7)	(1.9)
Mark-to-Market of Risk Management Contracts	(6.3)	17.3
Property Taxes	78.3	74.4
Change in Other Noncurrent Assets	(20.9)	(61.5)
Change in Other Noncurrent Liabilities	3.8	(36.4)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(31.8)	(19.9)
Fuel, Materials and Supplies	(3.7)	(10.2)
Accounts Payable	(6.4)	35.5
Accrued Taxes, Net	(144.7)	(141.9)
Other Current Assets	(0.2)	(2.0)
Other Current Liabilities	(2.0)	(8.4)
Net Cash Flows from (Used for) Operating Activities	11.2	3.5
Investing Activities
Construction Expenditures	(178.2)	(232.8)
Change in Advances to Affiliates, Net	(0.5)	0.0
Other Investing Activities	2.6	5.9
Net Cash Flows from (Used for) Investing Activities	(176.1)	(226.9)
Financing Activities
Issuance of Long-term Debt	445.8	347.1
Change in Advances from Affiliates, Net	(259.2)	(101.6)
Principal Payments for Finance Leases Obligations	(1.2)	(1.2)
Dividends Paid on Common Stock	(21.9)	(21.9)
Other Financing Activities	0.1	0.4
Net Cash Flows from (Used for) Financing Activities	163.6	222.8
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(1.3)	(0.6)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	7.4	3.7
Cash and Cash Equivalents at Beginning of Period	7.4
Cash, Cash Equivalents and Restricted Cash at End of Period	6.1	3.1
Cash and Cash Equivalents at End of Period	6.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	15.8	16.7
Noncash Acquisitions Under Finance Leases	0.4	4.3
Construction Expenditures Included in Current Liabilities as of March 31,	72.4	72.9
Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	(2.7)	(10.3)
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	49.9	44.7
Deferred Income Taxes	(0.8)	(5.3)
Allowance for Equity Funds Used During Construction	(0.4)	(1.0)
Mark-to-Market of Risk Management Contracts	4.8	9.5
Property Taxes	(32.8)	(29.8)
Deferred Fuel Over/Under-Recovery, Net	(703.5)	4.1
Change in Other Noncurrent Assets	(7.3)	(0.1)
Change in Other Noncurrent Liabilities	1.5	4.2
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(11.2)	0.9
Fuel, Materials and Supplies	4.5	(8.5)
Accounts Payable	15.2	(39.1)
Accrued Taxes, Net	22.4	25.1
Other Current Assets	(0.3)	(1.7)
Other Current Liabilities	(24.7)	(7.2)
Net Cash Flows from (Used for) Operating Activities	(685.4)	(14.5)
Investing Activities
Construction Expenditures	(79.9)	(96.5)
Change in Advances to Affiliates, Net	0.0	38.8
Other Investing Activities	0.5	1.6
Net Cash Flows from (Used for) Investing Activities	(79.4)	(56.1)
Financing Activities
Capital Contributions from Parent	425.0	0.0
Issuance of Long-term Debt	500.0	0.0
Change in Advances from Affiliates, Net	90.3	70.9
Retirement of Long-term Debt	(250.1)	(0.1)
Principal Payments for Finance Leases Obligations	(0.9)	(0.8)
Other Financing Activities	0.3	0.2
Net Cash Flows from (Used for) Financing Activities	764.6	70.2
Net Increase (Decrease) in Cash and Cash Equivalents	(0.2)	(0.4)
Cash and Cash Equivalents at Beginning of Period	2.6	1.5
Cash and Cash Equivalents at End of Period	2.4	1.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	16.9	16.7
Noncash Acquisitions Under Finance Leases	1.0	0.9
Construction Expenditures Included in Current Liabilities as of March 31,	22.2	30.8
Southwestern Electric Power Co [Member]
Operating Activities
Net Income (Loss)	63.4	16.1
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	69.6	67.3
Deferred Income Taxes	8.6	(9.2)
Allowance for Equity Funds Used During Construction	(2.1)	(1.4)
Mark-to-Market of Risk Management Contracts	1.1	3.9
Property Taxes	(61.6)	(49.0)
Deferred Fuel Over/Under-Recovery, Net	(461.1)	21.0
Change in Regulatory Assets	(89.1)	(15.1)
Change in Other Noncurrent Assets	6.1	11.1
Change in Other Noncurrent Liabilities	16.6	9.8
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(105.8)	11.3
Fuel, Materials and Supplies	0.4	(7.6)
Accounts Payable	95.1	(31.2)
Accrued Taxes, Net	73.9	51.2
Other Current Assets	8.2	(4.0)
Other Current Liabilities	(51.0)	(48.4)
Net Cash Flows from (Used for) Operating Activities	(427.7)	25.8
Investing Activities
Construction Expenditures	(91.4)	(122.4)
Other Investing Activities	0.1	0.8
Net Cash Flows from (Used for) Investing Activities	(91.3)	(121.6)
Financing Activities
Capital Contributions from Parent	100.0	0.0
Issuance of Long-term Debt	496.8	0.0
Change in Short-term Debt with Original Maturities less than 90 Days, Net	(30.0)	12.2
Change in Advances from Affiliates, Net	(37.7)	88.2
Retirement of Long-term Debt	(1.6)	(1.6)
Principal Payments for Finance Leases Obligations	(2.6)	(2.7)
Dividends Paid on Common Stock	(1.0)	(0.7)
Other Financing Activities	0.1	0.2
Net Cash Flows from (Used for) Financing Activities	524.0	95.6
Net Increase (Decrease) in Cash and Cash Equivalents	5.0	(0.2)
Cash and Cash Equivalents at Beginning of Period	13.2	1.6
Cash and Cash Equivalents at End of Period	18.2	1.4
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	39.7	40.7
Noncash Acquisitions Under Finance Leases	1.5	3.0
Construction Expenditures Included in Current Liabilities as of March 31,	40.2	45.2
Noncontrolling Interest [Member]
Supplementary Information
Noncontrolling Interest Assumed with Dry Lake Solar Project Acquisition	$ 18.9	$ 0.0