Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities
Net Income (Loss)	$ 1,949.5	$ 1,762.0
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	2,103.9	1,996.3
Rockport Plant, Unit 2 Operating Lease Amortization	100.8	102.4
Deferred Income Taxes	191.1	142.5
Allowance for Equity Funds Used During Construction	(103.9)	(111.7)
Mark-to-Market of Risk Management Contracts	101.0	46.4
Amortization of Nuclear Fuel	61.9	67.2
Pension Contributions to Qualified Plan Trust	0.0	(110.3)
Property Taxes	415.1	396.9
Deferred Fuel Over/Under-Recovery, Net	(1,356.8)	27.4
Change in Other Noncurrent Assets	(270.7)	(322.0)
Change in Other Noncurrent Liabilities	162.7	(25.1)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(199.2)	(138.9)
Fuel, Materials and Supplies	347.4	(97.4)
Accounts Payable	107.6	21.9
Accrued Taxes, Net	(471.1)	(502.9)
Rockport Plant, Unit 2 Operating Lease	(73.9)	(73.9)
Other Current Assets	(33.3)	26.0
Other Current Liabilities	(59.1)	(284.6)
Net Cash Flows from (Used for) Operating Activities	2,973.0	2,922.2
Investing Activities
Construction Expenditures	(4,087.0)	(4,690.4)
Purchases of Investment Securities	(1,612.3)	(1,329.5)
Sales of Investment Securities	1,571.7	1,293.0
Acquisitions of Nuclear Fuel	(63.2)	(68.4)
Other Investing Activities	51.8	88.0
Net Cash Flows from (Used for) Investing Activities	(4,906.2)	(4,707.3)
Financing Activities
Issuance of Common Stock	548.0	136.5
Issuance of Long-term Debt	5,062.3	3,985.8
Issuance of Short-term Debt with Original Maturities greater than 90 Days	1,178.5	1,304.5
Change in Short-term Debt with Original Maturities less than 90 Days, Net	(632.5)	(1,445.8)
Retirement of Long-term Debt	(1,549.8)	(700.5)
Redemption of Short-term Debt with Original Maturities Greater than 90 Days	(521.3)	(300.0)
Principal Payments for Finance Leases Obligations	(45.3)	(46.3)
Dividends Paid on Common Stock	(1,122.7)	(1,055.7)
Redemption of Noncontrolling Interest in Trent & Desert Sky Windfarms	0.0	(56.5)
Other Financing Activities	4.4	(5.7)
Net Cash Flows from (Used for) Financing Activities	2,921.6	1,816.3
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	988.4	31.2
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	1,426.7	463.8
Cash and Cash Equivalents at End of Period	1,372.7
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	775.2	690.5
Net Cash Paid (Received) for Income Taxes	9.3	(23.9)
Noncash Acquisitions Under Finance Leases	23.0	33.0
Construction Expenditures Included in Current Liabilities as of September 30,	764.1	830.1
Construction Expenditures Included in Noncurrent Liabilities as of September 30,	0.0	8.3
Acquisition of Nuclear Fuel Included in Current Liabilities as of September 30,	0.3	1.0
Noncash Contribution of Assets to Cedar Creek Project	(9.3)	0.0
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	0.6	2.4
Retained Earnings [Member]
Supplementary Information
Forward Equity Purchase Contract Included in Current and Noncurrent Liabilities as of September 30,	0.0	120.6
Dry Lake Solar Project
Investing Activities
Acquisitions of Assets	(114.4)	0.0
North Central Wind Energy Facilities
Investing Activities
Acquisitions of Assets	(652.8)	0.0
AEP Texas Inc. [Member]
Operating Activities
Net Income (Loss)	225.4	197.1
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	287.1	435.8
Deferred Income Taxes	45.8	(11.5)
Allowance for Equity Funds Used During Construction	(16.7)	(14.4)
Mark-to-Market of Risk Management Contracts	0.0	0.1
Pension Contributions to Qualified Plan Trust	0.0	(11.3)
Change in Other Noncurrent Assets	(73.4)	(77.3)
Change in Other Noncurrent Liabilities	17.5	(30.0)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(40.2)	(40.2)
Fuel, Materials and Supplies	(2.5)	(9.4)
Accounts Payable	(10.9)	24.2
Accrued Taxes, Net	29.5	73.4
Other Current Assets	(2.0)	(0.8)
Other Current Liabilities	(5.0)	(49.8)
Net Cash Flows from (Used for) Operating Activities	454.6	485.9
Investing Activities
Construction Expenditures	(742.4)	(976.1)
Change in Advances to Affiliates, Net	(47.5)	58.8
Other Investing Activities	29.6	24.1
Net Cash Flows from (Used for) Investing Activities	(760.3)	(893.2)
Financing Activities
Issuance of Long-term Debt	444.2	652.8
Change in Short-term Debt with Original Maturities less than 90 Days, Net	0.0	2.0
Change in Advances from Affiliates, Net	(67.1)	0.0
Retirement of Long-term Debt	(52.2)	(356.5)
Principal Payments for Finance Leases Obligations	(5.0)	(4.7)
Other Financing Activities	1.0	0.8
Net Cash Flows from (Used for) Financing Activities	320.9	294.4
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	15.2	(112.9)
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	44.0	44.9
Cash and Cash Equivalents at End of Period	0.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	110.0	102.0
Net Cash Paid (Received) for Income Taxes	(8.4)	(55.6)
Noncash Acquisitions Under Finance Leases	3.3	5.1
Construction Expenditures Included in Current Liabilities as of September 30,	134.9	167.6
AEP Transmission Co [Member]
Operating Activities
Net Income (Loss)	445.7	309.1
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	219.0	176.4
Deferred Income Taxes	46.8	65.4
Allowance for Equity Funds Used During Construction	(49.3)	(54.9)
Property Taxes	154.0	136.3
Change in Other Noncurrent Assets	2.3	(1.5)
Change in Other Noncurrent Liabilities	8.3	19.5
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(23.6)	(30.1)
Fuel, Materials and Supplies	(0.5)	0.2
Accounts Payable	(10.7)	26.0
Accrued Taxes, Net	(138.8)	(139.0)
Accrued Interest	26.3	29.0
Other Current Assets	0.5	9.1
Other Current Liabilities	(3.6)	(10.7)
Net Cash Flows from (Used for) Operating Activities	676.4	534.8
Investing Activities
Construction Expenditures	(1,070.8)	(1,163.8)
Change in Advances to Affiliates, Net	29.9	(21.3)
Other Investing Activities	(7.9)	1.1
Net Cash Flows from (Used for) Investing Activities	(1,048.8)	(1,184.0)
Financing Activities
Capital Contributions from Parent	184.0	185.0
Issuance of Long-term Debt	443.7	519.4
Change in Advances from Affiliates, Net	(142.8)	(50.2)
Dividends Paid on Common Stock	(112.5)	(5.0)
Net Cash Flows from (Used for) Financing Activities	372.4	649.2
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	75.8	63.3
Net Cash Paid (Received) for Income Taxes	37.6	1.9
Construction Expenditures Included in Current Liabilities as of September 30,	206.8	283.6
Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	275.1	313.2
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	406.6	366.0
Deferred Income Taxes	(12.0)	(28.2)
Allowance for Equity Funds Used During Construction	(12.1)	(11.5)
Mark-to-Market of Risk Management Contracts	(26.8)	8.0
Pension Contributions to Qualified Plan Trust	0.0	(7.0)
Deferred Fuel Over/Under-Recovery, Net	(43.9)	38.8
Change in Other Noncurrent Assets	(39.2)	5.4
Change in Other Noncurrent Liabilities	20.2	(26.0)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	38.1	7.2
Fuel, Materials and Supplies	126.3	12.4
Accounts Payable	26.5	(74.0)
Accrued Taxes, Net	(48.0)	1.9
Other Current Assets	(20.7)	10.1
Other Current Liabilities	0.5	(9.7)
Net Cash Flows from (Used for) Operating Activities	690.6	606.6
Investing Activities
Construction Expenditures	(586.4)	(566.6)
Change in Advances to Affiliates, Net	(163.8)	(137.4)
Other Investing Activities	12.4	4.6
Net Cash Flows from (Used for) Investing Activities	(737.8)	(699.4)
Financing Activities
Issuance of Long-term Debt	494.0	557.2
Change in Advances from Affiliates, Net	(18.6)	(232.4)
Retirement of Long-term Debt	(393.0)	(90.3)
Principal Payments for Finance Leases Obligations	(5.8)	(5.6)
Dividends Paid on Common Stock	(37.5)	(150.0)
Other Financing Activities	0.5	0.3
Net Cash Flows from (Used for) Financing Activities	39.6	79.2
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(7.6)	(13.6)
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	15.1	13.2
Cash and Cash Equivalents at End of Period	5.0
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	124.2	130.0
Net Cash Paid (Received) for Income Taxes	52.6	(10.7)
Noncash Acquisitions Under Finance Leases	1.3	3.0
Construction Expenditures Included in Current Liabilities as of September 30,	92.3	90.0
Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	232.1	232.8
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	328.7	303.6
Rockport Plant, Unit 2 Operating Lease Amortization	51.1	51.9
Deferred Income Taxes	(36.6)	(6.1)
Amortization (Deferral) of Incremental Nuclear Refueling Outage Expenses, Net	(2.5)	21.3
Allowance for Equity Funds Used During Construction	(9.7)	(8.8)
Mark-to-Market of Risk Management Contracts	0.5	5.6
Amortization of Nuclear Fuel	61.9	67.2
Pension Contributions to Qualified Plan Trust	0.0	(6.4)
Deferred Fuel Over/Under-Recovery, Net	(18.0)	23.4
Change in Other Noncurrent Assets	7.3	40.8
Change in Other Noncurrent Liabilities	(10.2)	30.2
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	18.2	32.2
Fuel, Materials and Supplies	43.0	(15.4)
Accounts Payable	20.1	(0.9)
Accrued Taxes, Net	(20.3)	(84.4)
Operating Lease, Payments	(36.9)	(36.9)
Other Current Assets	(0.7)	6.6
Other Current Liabilities	(28.0)	(59.1)
Net Cash Flows from (Used for) Operating Activities	600.0	597.6
Investing Activities
Construction Expenditures	(370.2)	(409.1)
Change in Advances to Affiliates, Net	(67.3)	(0.1)
Purchases of Investment Securities	(1,586.3)	(1,290.0)
Sales of Investment Securities	1,556.6	1,257.1
Acquisitions of Nuclear Fuel	(63.2)	(68.4)
Other Investing Activities	12.9	8.3
Net Cash Flows from (Used for) Investing Activities	(517.5)	(502.2)
Financing Activities
Issuance of Long-term Debt	507.0	0.0
Change in Advances from Affiliates, Net	(103.0)	44.7
Retirement of Long-term Debt	(307.2)	(71.1)
Principal Payments for Finance Leases Obligations	(4.9)	(4.8)
Dividends Paid on Common Stock	(175.0)	(63.7)
Other Financing Activities	0.5	0.3
Net Cash Flows from (Used for) Financing Activities	(82.6)	(94.6)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.1)	0.8
Cash and Cash Equivalents at Beginning of Period	3.3	2.0
Cash and Cash Equivalents at End of Period	3.2	2.8
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	93.9	97.5
Net Cash Paid (Received) for Income Taxes	11.8	59.7
Noncash Acquisitions Under Finance Leases	3.1	1.9
Construction Expenditures Included in Current Liabilities as of September 30,	59.0	57.6
Acquisition of Nuclear Fuel Included in Current Liabilities as of September 30,	0.3	1.0
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	0.6	2.4
Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	198.6	215.0
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	228.6	204.4
Deferred Income Taxes	29.3	35.6
Carrying Costs Income	(1.1)	(1.3)
Allowance for Equity Funds Used During Construction	(7.6)	(9.3)
Mark-to-Market of Risk Management Contracts	(19.9)	9.7
Pension Contributions to Qualified Plan Trust		(0.1)
Property Taxes	234.9	225.1
Change in Other Noncurrent Assets	(1.1)	(93.8)
Change in Other Noncurrent Liabilities	4.6	(58.3)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	20.7	33.4
Fuel, Materials and Supplies	(0.6)	(19.8)
Accounts Payable	(19.1)	(19.9)
Increase (Decrease) in Contract with Customer, Liability	68.4	12.4
Accrued Taxes, Net	(289.7)	(266.2)
Other Current Assets	(7.8)	(2.5)
Other Current Liabilities	5.8	(35.7)
Net Cash Flows from (Used for) Operating Activities	445.1	230.1
Investing Activities
Construction Expenditures	(536.6)	(604.6)
Change in Advances to Affiliates, Net	(622.9)	0.0
Other Investing Activities	10.7	14.1
Net Cash Flows from (Used for) Investing Activities	(1,148.8)	(590.5)
Financing Activities
Issuance of Long-term Debt	1,037.5	347.0
Change in Advances from Affiliates, Net	(259.2)	84.9
Retirement of Long-term Debt	(0.1)	(0.1)
Principal Payments for Finance Leases Obligations	(3.7)	(3.5)
Dividends Paid on Common Stock	(71.9)	(65.6)
Other Financing Activities	0.5	0.6
Net Cash Flows from (Used for) Financing Activities	703.1	363.3
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(0.6)	2.9
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	6.8	6.6
Cash and Cash Equivalents at End of Period	6.8
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	78.6	69.7
Net Cash Paid (Received) for Income Taxes	0.3	(6.0)
Noncash Acquisitions Under Finance Leases	1.4	5.2
Construction Expenditures Included in Current Liabilities as of September 30,	66.5	75.9
Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	136.6	116.4
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	149.0	129.8
Deferred Income Taxes	109.8	(3.2)
Allowance for Equity Funds Used During Construction	(1.5)	(3.2)
Mark-to-Market of Risk Management Contracts	(8.2)	(0.3)
Property Taxes	(10.9)	(10.6)
Deferred Fuel Over/Under-Recovery, Net	(776.4)	(46.6)
Change in Other Noncurrent Assets	(12.8)	(7.2)
Change in Other Noncurrent Liabilities	4.5	6.1
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(13.4)	(5.6)
Fuel, Materials and Supplies	9.9	(17.2)
Accounts Payable	16.4	(26.1)
Accrued Taxes, Net	9.3	36.9
Other Current Assets	(5.9)	(0.1)
Other Current Liabilities	(18.4)	(16.4)
Net Cash Flows from (Used for) Operating Activities	(412.0)	152.7
Investing Activities
Construction Expenditures	(219.6)	(256.4)
Change in Advances to Affiliates, Net	(59.5)	38.8
Acquisitions of Assets	297.0	0.0
Other Investing Activities	1.9	3.9
Net Cash Flows from (Used for) Investing Activities	(574.2)	(213.7)
Financing Activities
Capital Contributions from Parent	625.0	0.0
Issuance of Long-term Debt	1,290.0	0.0
Change in Advances from Affiliates, Net	(155.4)	77.8
Retirement of Long-term Debt	(750.4)	(13.0)
Principal Payments for Finance Leases Obligations	(2.5)	(2.7)
Dividends Paid on Common Stock	(20.0)	0.0
Other Financing Activities	0.5	0.4
Net Cash Flows from (Used for) Financing Activities	987.2	62.5
Net Increase (Decrease) in Cash and Cash Equivalents	1.0	1.5
Cash and Cash Equivalents at Beginning of Period	2.6	1.5
Cash and Cash Equivalents at End of Period	3.6	3.0
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	42.9	45.5
Net Cash Paid (Received) for Income Taxes	(101.2)	(9.5)
Noncash Acquisitions Under Finance Leases	3.1	3.0
Construction Expenditures Included in Current Liabilities as of September 30,	44.2	23.5
Southwestern Electric Power Co [Member]
Operating Activities
Net Income (Loss)	210.7	163.9
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	217.4	203.9
Deferred Income Taxes	22.5	(0.3)
Allowance for Equity Funds Used During Construction	(5.4)	(5.7)
Mark-to-Market of Risk Management Contracts	(18.1)	(2.3)
Pension Contributions to Qualified Plan Trust	0.0	(8.9)
Property Taxes	(20.0)	(16.5)
Deferred Fuel Over/Under-Recovery, Net	(506.8)	16.3
Change in Regulatory Assets	(91.5)	(64.5)
Change in Other Noncurrent Assets	38.3	3.2
Change in Other Noncurrent Liabilities	40.0	21.0
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(70.2)	8.0
Fuel, Materials and Supplies	115.1	(70.9)
Accounts Payable	(21.1)	88.0
Accrued Taxes, Net	72.2	46.6
Other Current Assets	4.2	1.3
Other Current Liabilities	(48.2)	(50.3)
Net Cash Flows from (Used for) Operating Activities	(60.9)	332.8
Investing Activities
Construction Expenditures	(277.2)	(319.5)
Acquisitions of Assets	355.8	0.0
Other Investing Activities	2.1	4.8
Net Cash Flows from (Used for) Investing Activities	(630.9)	(314.7)
Financing Activities
Capital Contributions from Parent	280.0	0.0
Issuance of Long-term Debt	496.4	0.0
Change in Short-term Debt with Original Maturities less than 90 Days, Net	(35.0)	23.7
Change in Advances from Affiliates, Net	(1.7)	11.9
Retirement of Long-term Debt	(4.7)	(19.7)
Principal Payments for Finance Leases Obligations	(8.1)	(8.0)
Dividends Paid on Common Stock	(3.8)	(2.3)
Other Financing Activities	0.5	0.3
Net Cash Flows from (Used for) Financing Activities	723.6	5.9
Net Increase (Decrease) in Cash and Cash Equivalents	31.8	24.0
Cash and Cash Equivalents at Beginning of Period	13.2	1.6
Cash and Cash Equivalents at End of Period	45.0	25.6
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	98.0	95.2
Net Cash Paid (Received) for Income Taxes	(11.3)	11.9
Noncash Acquisitions Under Finance Leases	4.4	5.9
Construction Expenditures Included in Current Liabilities as of September 30,	46.8	50.6
Noncontrolling Interest [Member]
Supplementary Information
Noncontrolling Interest Assumed - Dry Lake Solar Project	$ 35.0	$ 0.0