Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating Activities
Net Income (Loss)	$ 499.3	$ 574.1
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	672.2	605.8
Deferred Income Taxes	27.9	16.8
Allowance for Equity Funds Used During Construction	(31.4)	(28.9)
Mark-to-Market of Risk Management Contracts	57.4	65.5
Amortization of Nuclear Fuel	23.4	25.1
Property Taxes	(59.8)	(75.6)
Deferred Fuel Over/Under-Recovery, Net	63.1	32.5
Recovery of Ohio Capacity Costs, Net	0.0	14.7
Refund of Global Settlement	0.0	(4.1)
Change in Other Noncurrent Assets	(50.8)	(47.9)
Change in Other Noncurrent Liabilities	(74.8)	67.3
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(32.6)	57.5
Fuel, Materials and Supplies	(35.8)	(26.4)
Accounts Payable	(111.1)	(152.6)
Accrued Taxes, Net	(93.9)	(77.0)
Other Current Assets	5.3	(18.8)
Other Current Liabilities	(242.7)	(219.7)
Net Cash Flows from (Used for) Operating Activities	615.7	808.3
Investing Activities
Construction Expenditures	(1,792.7)	(1,565.4)
Purchases of Investment Securities	(632.7)	(130.4)
Sales of Investment Securities	635.6	111.9
Acquisitions of Nuclear Fuel	(1.3)	(32.4)
Other Investing Activities	25.1	33.5
Net Cash Flows from (Used for) Investing Activities	(1,766.0)	(1,582.8)
Financing Activities
Issuance of Common Stock, Net	56.1	14.5
Issuance of Long-term Debt	1,418.9	1,285.6
Issuance of Short-term Debt with Original Maturities greater than 90 Days	1,297.5	0.0
Change in Short-term Debt with Original Maturities less than 90 Days, Net	328.3	(52.0)
Retirement of Long-term Debt	(300.5)	(220.6)
Principal Payments for Finance Leases	(15.4)	(14.3)
Dividends Paid on Common Stock	(363.7)	(333.6)
Other Financing Activities	(32.7)	13.9
Net Cash Flows from (Used for) Financing Activities	2,388.5	693.5
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	1,238.2	(81.0)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	432.6	444.1
Cash and Cash Equivalents at Beginning of Period	246.8
Cash, Cash Equivalents and Restricted Cash at End of Period	1,670.8	363.1
Cash and Cash Equivalents at End of Period	1,554.6
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	212.6	168.9
Net Cash Paid (Received) for Income Taxes	(0.6)	(0.6)
Noncash Acquisitions Under Finance Leases	19.4	23.1
Construction Expenditures Included in Current Liabilities as of March 31,	874.1	846.3
Construction Expenditures Included in Noncurrent Liabilities as of March 31,	8.3	0.0
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	1.3	1.0
Stockholders' Equity, Other	30.2	55.6
AEP Texas Inc. [Member]
Operating Activities
Net Income (Loss)	47.6	34.4
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	162.5	138.9
Deferred Income Taxes	(7.6)	(11.0)
Allowance for Equity Funds Used During Construction	(5.1)	(1.8)
Property Taxes	(69.3)	(73.8)
Change in Other Noncurrent Assets	(10.8)	(3.2)
Change in Other Noncurrent Liabilities	3.2	(5.7)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(34.3)	(7.8)
Fuel, Materials and Supplies	(7.6)	(1.0)
Accounts Payable	2.4	4.2
Accrued Taxes, Net	38.9	57.5
Other Current Assets	(1.4)	0.5
Other Current Liabilities	(4.6)	(4.4)
Net Cash Flows from (Used for) Operating Activities	113.9	126.8
Investing Activities
Construction Expenditures	(327.5)	(343.1)
Change in Advances to Affiliates, Net	200.1	0.3
Other Investing Activities	7.4	6.2
Net Cash Flows from (Used for) Investing Activities	(120.0)	(336.6)
Financing Activities
Capital Contributions from Parent	0.0	200.0
Change in Advances from Affiliates, Net	63.9	55.2
Retirement of Long-term Debt	(114.3)	(103.5)
Principal Payments for Finance Leases	(1.5)	(1.2)
Other Financing Activities	0.4	0.2
Net Cash Flows from (Used for) Financing Activities	(51.5)	150.7
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(57.6)	(59.1)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	157.8	159.8
Cash and Cash Equivalents at Beginning of Period	3.1
Cash, Cash Equivalents and Restricted Cash at End of Period	100.2	100.7
Cash and Cash Equivalents at End of Period	0.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	21.1	22.4
Net Cash Paid (Received) for Income Taxes	0.0	(5.6)
Noncash Acquisitions Under Finance Leases	3.7	2.4
Construction Expenditures Included in Current Liabilities as of March 31,	175.1	195.7
AEP Transmission Co [Member]
Operating Activities
Net Income (Loss)	117.8	104.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	56.0	40.3
Deferred Income Taxes	13.7	14.5
Allowance for Equity Funds Used During Construction	(16.2)	(11.3)
Property Taxes	28.4	23.2
Change in Other Noncurrent Assets	2.4	2.7
Change in Other Noncurrent Liabilities	0.6	2.2
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(22.0)	(8.2)
Fuel, Materials and Supplies	0.4	(0.6)
Accounts Payable	22.7	11.4
Accrued Taxes, Net	(37.8)	(32.1)
Accrued Interest	19.4	19.2
Other Current Assets	0.4	0.4
Other Current Liabilities	1.2	0.2
Net Cash Flows from (Used for) Operating Activities	187.0	166.2
Investing Activities
Construction Expenditures	(491.5)	(365.0)
Change in Advances to Affiliates, Net	(43.0)	23.4
Acquisitions of Assets	(1.7)	(2.5)
Other Investing Activities	3.8	0.3
Net Cash Flows from (Used for) Investing Activities	(532.4)	(343.8)
Financing Activities
Capital Contributions from Parent	185.0	0.0
Change in Advances from Affiliates, Net	160.4	177.7
Other Financing Activities	0.0	(0.1)
Net Cash Flows from (Used for) Financing Activities	345.4	177.6
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	9.3	1.6
Net Cash Paid (Received) for Income Taxes	0.1	(1.2)
Construction Expenditures Included in Current Liabilities as of March 31,	290.6	261.1
Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	115.3	133.7
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	122.2	112.5
Deferred Income Taxes	(5.1)	(45.0)
Allowance for Equity Funds Used During Construction	(2.4)	(1.7)
Mark-to-Market of Risk Management Contracts	29.6	50.6
Deferred Fuel Over/Under-Recovery, Net	7.6	20.8
Change in Other Noncurrent Assets	(24.4)	(12.1)
Change in Other Noncurrent Liabilities	(16.1)	(20.5)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(2.6)	19.5
Fuel, Materials and Supplies	(5.5)	(9.6)
Accounts Payable	(86.6)	(8.3)
Accrued Taxes, Net	14.5	13.7
Other Current Assets	19.2	(0.8)
Other Current Liabilities	(11.1)	(2.3)
Net Cash Flows from (Used for) Operating Activities	154.6	250.5
Investing Activities
Construction Expenditures	(219.1)	(205.1)
Change in Advances to Affiliates, Net	0.3	(193.6)
Other Investing Activities	1.1	15.2
Net Cash Flows from (Used for) Investing Activities	(217.7)	(383.5)
Financing Activities
Issuance of Long-term Debt	0.0	393.3
Change in Advances from Affiliates, Net	118.6	(205.6)
Retirement of Long-term Debt	(12.2)	(12.0)
Principal Payments for Finance Leases	(1.8)	(1.6)
Dividends Paid on Common Stock	(50.0)	(50.0)
Other Financing Activities	0.2	0.3
Net Cash Flows from (Used for) Financing Activities	54.8	124.4
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(8.3)	(8.6)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	26.8	29.8
Cash and Cash Equivalents at Beginning of Period	3.3
Cash, Cash Equivalents and Restricted Cash at End of Period	18.5	21.2
Cash and Cash Equivalents at End of Period	2.8
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	31.9	14.5
Net Cash Paid (Received) for Income Taxes	0.0	8.0
Noncash Acquisitions Under Finance Leases	1.9	2.1
Construction Expenditures Included in Current Liabilities as of March 31,	103.7	87.8
Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	92.3	98.9
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	93.9	86.2
Deferred Income Taxes	(16.3)	(13.9)
Deferral of Incremental Nuclear Refueling Outage Expenses, Net	15.2	(14.8)
Allowance for Equity Funds Used During Construction	(2.0)	(6.2)
Mark-to-Market of Risk Management Contracts	4.4	4.7
Amortization of Nuclear Fuel	23.4	25.1
Deferred Fuel Over/Under-Recovery, Net	22.5	(5.2)
Change in Other Noncurrent Assets	14.4	13.5
Change in Other Noncurrent Liabilities	10.0	5.2
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	8.6	16.0
Fuel, Materials and Supplies	(16.2)	6.6
Accounts Payable	(21.6)	(3.1)
Accrued Taxes, Net	25.0	25.6
Other Current Assets	18.2	1.4
Other Current Liabilities	(62.7)	(35.2)
Net Cash Flows from (Used for) Operating Activities	209.1	204.8
Investing Activities
Construction Expenditures	(141.4)	(149.3)
Change in Advances to Affiliates, Net	(0.1)	(0.1)
Purchases of Investment Securities	(626.0)	(130.3)
Sales of Investment Securities	612.4	111.9
Acquisitions of Nuclear Fuel	(1.3)	(32.4)
Other Investing Activities	4.2	8.6
Net Cash Flows from (Used for) Investing Activities	(152.2)	(191.6)
Financing Activities
Change in Advances from Affiliates, Net	(10.7)	33.6
Retirement of Long-term Debt	(23.7)	(26.5)
Principal Payments for Finance Leases	(1.5)	(1.2)
Dividends Paid on Common Stock	(21.3)	(20.0)
Other Financing Activities	0.1	0.2
Net Cash Flows from (Used for) Financing Activities	(57.1)	(13.9)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.2)	(0.7)
Cash and Cash Equivalents at Beginning of Period	2.0	2.4
Cash and Cash Equivalents at End of Period	1.8	1.7
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	44.3	43.3
Net Cash Paid (Received) for Income Taxes	0.0	(3.3)
Noncash Acquisitions Under Finance Leases	1.4	1.7
Construction Expenditures Included in Current Liabilities as of March 31,	67.8	80.0
Acquisition of Nuclear Fuel Included in Current Liabilities as of March 31,	0.0	1.0
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	1.3	7.9
Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	75.1	128.0
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	70.5	63.3
Amortization Of Generation Deferrals	0.0	32.4
Deferred Income Taxes	12.9	10.1
Carrying Costs Income	(0.4)	(0.2)
Allowance for Equity Funds Used During Construction	(1.9)	(5.2)
Mark-to-Market of Risk Management Contracts	17.3	6.7
Property Taxes	74.4	66.0
Refund of Global Settlement	0.0	(4.1)
Reversal of a Regulatory Provision	0.0	(56.2)
Change in Other Noncurrent Assets	(61.5)	(7.5)
Change in Other Noncurrent Liabilities	(36.4)	17.6
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(19.9)	31.7
Fuel, Materials and Supplies	(10.2)	(3.4)
Accounts Payable	35.5	(23.9)
Accrued Taxes, Net	(141.9)	(114.4)
Other Current Assets	(2.0)	(7.7)
Other Current Liabilities	(8.4)	(16.2)
Net Cash Flows from (Used for) Operating Activities	3.5	117.2
Investing Activities
Construction Expenditures	(232.8)	(198.5)
Other Investing Activities	5.9	3.7
Net Cash Flows from (Used for) Investing Activities	(226.9)	(194.8)
Financing Activities
Issuance of Long-term Debt	347.1	0.0
Change in Advances from Affiliates, Net	(101.6)	113.5
Retirement of Long-term Debt	0.0	(23.4)
Principal Payments for Finance Leases	(1.2)	(0.7)
Dividends Paid on Common Stock	(21.9)	(25.0)
Other Financing Activities	0.4	0.5
Net Cash Flows from (Used for) Financing Activities	222.8	64.9
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(0.6)	(12.7)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	3.7	32.5
Cash and Cash Equivalents at Beginning of Period	3.7
Cash, Cash Equivalents and Restricted Cash at End of Period	3.1	19.8
Cash and Cash Equivalents at End of Period	3.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	16.7	17.0
Net Cash Paid (Received) for Income Taxes	0.0	(0.2)
Noncash Acquisitions Under Finance Leases	4.3	3.2
Construction Expenditures Included in Current Liabilities as of March 31,	72.9	72.8
Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	(10.3)	6.2
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	44.7	43.5
Deferred Income Taxes	(5.3)	(5.8)
Allowance for Equity Funds Used During Construction	(1.0)	(0.1)
Mark-to-Market of Risk Management Contracts	9.5	5.1
Property Taxes	(29.8)	(29.9)
Deferred Fuel Over/Under-Recovery, Net	4.1	(2.4)
Change in Other Noncurrent Assets	(0.1)	8.0
Change in Other Noncurrent Liabilities	4.2	(0.7)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	0.9	2.0
Fuel, Materials and Supplies	(8.5)	3.2
Accounts Payable	(39.1)	(23.3)
Accrued Taxes, Net	25.1	25.3
Other Current Assets	(1.7)	(3.8)
Other Current Liabilities	(7.2)	4.4
Net Cash Flows from (Used for) Operating Activities	(14.5)	31.7
Investing Activities
Construction Expenditures	(96.5)	(70.7)
Change in Advances to Affiliates, Net	38.8	0.0
Other Investing Activities	1.6	0.4
Net Cash Flows from (Used for) Investing Activities	(56.1)	(70.3)
Financing Activities
Issuance of Long-term Debt	0.0	99.9
Change in Advances from Affiliates, Net	70.9	(50.3)
Retirement of Long-term Debt	(0.1)	(0.1)
Principal Payments for Finance Leases	(0.8)	(0.7)
Dividends Paid on Common Stock	0.0	(11.3)
Other Financing Activities	0.2	0.6
Net Cash Flows from (Used for) Financing Activities	70.2	38.1
Net Increase (Decrease) in Cash and Cash Equivalents	(0.4)	(0.5)
Cash and Cash Equivalents at Beginning of Period	1.5	2.0
Cash and Cash Equivalents at End of Period	1.1	1.5
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	16.7	10.9
Net Cash Paid (Received) for Income Taxes	0.0	0.6
Noncash Acquisitions Under Finance Leases	0.9	1.1
Construction Expenditures Included in Current Liabilities as of March 31,	30.8	15.6
Southwestern Electric Power Co [Member]
Operating Activities
Net Income (Loss)	16.1	29.0
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	67.3	62.1
Deferred Income Taxes	(9.2)	(2.5)
Allowance for Equity Funds Used During Construction	(1.4)	(1.8)
Mark-to-Market of Risk Management Contracts	3.9	2.3
Property Taxes	(49.0)	(48.9)
Deferred Fuel Over/Under-Recovery, Net	21.0	10.3
Change in Other Noncurrent Assets	(4.0)	2.9
Change in Other Noncurrent Liabilities	9.8	7.9
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	11.3	6.3
Fuel, Materials and Supplies	(7.6)	(16.2)
Accounts Payable	(31.2)	(55.0)
Accrued Taxes, Net	51.2	52.7
Accrued Interest	(12.7)	(12.7)
Other Current Assets	(4.0)	(10.0)
Other Current Liabilities	(35.7)	(17.0)
Net Cash Flows from (Used for) Operating Activities	25.8	9.4
Investing Activities
Construction Expenditures	(122.4)	(86.6)
Change in Advances to Affiliates, Net	0.0	81.4
Other Investing Activities	0.8	(3.1)
Net Cash Flows from (Used for) Investing Activities	(121.6)	(8.3)
Financing Activities
Change in Short-term Debt with Original Maturities less than 90 Days, Net	12.2	0.0
Change in Advances from Affiliates, Net	88.2	74.0
Retirement of Long-term Debt	(1.6)	(55.1)
Principal Payments for Finance Leases	(2.7)	(2.7)
Dividends Paid on Common Stock	0.0	(18.7)
Dividends Paid on Common Stock	(0.7)	(1.1)
Other Financing Activities	0.2	0.1
Net Cash Flows from (Used for) Financing Activities	95.6	(3.5)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.2)	(2.4)
Cash and Cash Equivalents at Beginning of Period	1.6	24.5
Cash and Cash Equivalents at End of Period	1.4	22.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	40.7	40.5
Net Cash Paid (Received) for Income Taxes	0.0	0.2
Noncash Acquisitions Under Finance Leases	3.0	0.8
Construction Expenditures Included in Current Liabilities as of March 31,	45.2	44.8
Retained Earnings [Member]
Supplementary Information
Stockholders' Equity, Other	0.0	62.1
Retained Earnings [Member] | AEP Texas Inc. [Member]
Operating Activities
Net Income (Loss)	47.6	34.4
Retained Earnings [Member] | AEP Transmission Co [Member]
Operating Activities
Net Income (Loss)	117.8	104.3
Retained Earnings [Member] | Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	115.3	133.7
Retained Earnings [Member] | Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	92.3	98.9
Retained Earnings [Member] | Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	75.1	128.0
Retained Earnings [Member] | Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	$ (10.3)	$ 6.2