Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net Income (Loss)	$ 456.7	$ 594.2
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	539.7	481.9
Deferred Income Taxes	87.3	136.2
Carrying Costs Income	(3.4)	(5.9)
Allowance for Equity Funds Used During Construction	(30.7)	(21.2)
Mark-to-Market of Risk Management Contracts	(0.7)	6.0
Amortization of Nuclear Fuel	27.4	35.1
Property Taxes	(63.7)	(44.4)
Deferred Fuel Over/Under-Recovery, Net	(61.2)	19.3
Gain on Sale of Merchant Generation Assets	0.0	(226.5)
Recovery of Ohio Capacity Costs	18.0	30.2
Provision for Refund - Global Settlement	(5.4)	0.0
Change in Other Noncurrent Assets	(59.8)	(99.1)
Change in Other Noncurrent Liabilities	133.3	45.0
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	39.7	235.8
Fuel, Materials and Supplies	28.5	13.4
Accounts Payable	(129.3)	(250.7)
Accrued Taxes, Net	(74.3)	186.8
Other Current Assets	(40.1)	(45.9)
Other Current Liabilities	(63.2)	(289.3)
Net Cash Flows from (Used for) Operating Activities	802.2	806.8
Investing Activities
Construction Expenditures	(1,905.8)	(1,365.8)
Purchases of Investment Securities	(525.9)	(506.0)
Sales of Investment Securities	508.6	487.9
Acquisitions of Nuclear Fuel	(23.8)	(3.7)
Proceeds from Sale of Merchant Generation Assets	0.0	2,159.6
Other Investing Activities	19.1	4.2
Net Cash Flows from (Used for) Investing Activities	(1,927.8)	776.2
Financing Activities
Issuance of Common Stock, Net	32.2	0.0
Issuance of Long-term Debt	841.0	82.9
Commercial Paper and Credit Facility Borrowings	205.6	0.0
Change in Short-term Debt, Net	814.6	(177.0)
Retirement of Long-term Debt	(544.0)	(1,242.3)
Make Whole Premium on Extinguishment of Long-term Debt	0.0	(44.9)
Principal Payments for Capital Lease Obligations	(16.8)	(16.6)
Dividends Paid on Common Stock	(306.1)	(291.4)
Other Financing Activities	3.0	2.2
Net Cash Flows from (Used for) Financing Activities	1,029.5	(1,687.1)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(96.1)	(104.1)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	412.6	403.5
Cash and Cash Equivalents at Beginning of Period	214.6
Cash, Cash Equivalents and Restricted Cash at End of Period	316.5	299.4
Cash and Cash Equivalents at End of Period	183.4
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	188.0	205.9
Net Cash Paid (Received) for Income Taxes	(0.9)	(88.8)
Noncash Acquisitions Under Capital Leases	21.4	11.4
Construction Expenditures Included in Current Liabilities as of March 31,	799.9	515.6
Noncash Contribution of Assets by Noncontrolling Interest	84.0	0.0
Expected Reimbursement For Spent Nuclear Fuel Dry Cask Storage	0.1	1.0
AEP Texas Inc. [Member]
Operating Activities
Net Income (Loss)	46.8	33.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	110.0	102.8
Deferred Income Taxes	(4.4)	40.8
Allowance for Equity Funds Used During Construction	(5.5)	(1.8)
Mark-to-Market of Risk Management Contracts	0.2	0.1
Property Taxes	(56.1)	(46.2)
Change in Other Noncurrent Assets	(12.7)	(12.7)
Change in Other Noncurrent Liabilities	6.5	4.8
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	1.8	3.7
Fuel, Materials and Supplies	(0.2)	0.4
Accounts Payable	(25.9)	(13.4)
Accrued Taxes, Net	25.2	(3.5)
Other Current Assets	(1.6)	(0.3)
Other Current Liabilities	(5.1)	(25.9)
Net Cash Flows from (Used for) Operating Activities	79.0	82.1
Investing Activities
Construction Expenditures	(481.6)	(200.2)
Change in Advances to Affiliates, Net	103.8	0.3
Other Investing Activities	13.4	4.6
Net Cash Flows from (Used for) Investing Activities	(364.4)	(195.3)
Financing Activities
Capital Contributions from Parent	100.0	200.0
Change in Advances from Affiliates, Net	232.7	(43.0)
Retirement of Long-term Debt	(96.5)	(89.9)
Principal Payments for Capital Lease Obligations	(1.1)	(0.9)
Other Financing Activities	0.3	0.6
Net Cash Flows from (Used for) Financing Activities	235.4	66.8
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(50.0)	(46.4)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	157.2	146.9
Cash and Cash Equivalents at Beginning of Period	2.0
Cash, Cash Equivalents and Restricted Cash at End of Period	107.2	100.5
Cash and Cash Equivalents at End of Period	0.1
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	27.8	33.7
Noncash Acquisitions Under Capital Leases	4.0	2.0
Construction Expenditures Included in Current Liabilities as of March 31,	169.3	65.5
AEP Transmission Co [Member]
Operating Activities
Net Income (Loss)	85.9	57.0
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	30.6	23.3
Deferred Income Taxes	15.7	74.1
Allowance for Equity Funds Used During Construction	(15.3)	(10.9)
Property Taxes	17.3	16.8
Change in Other Noncurrent Assets	2.7	2.2
Change in Other Noncurrent Liabilities	23.9	8.3
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(10.1)	(39.0)
Fuel, Materials and Supplies	(1.9)	(3.8)
Accounts Payable	(12.3)	(8.2)
Accrued Taxes, Net	(33.6)	(79.1)
Accrued Interest	23.3	17.6
Other Current Assets	0.3	0.2
Other Current Liabilities	0.6	0.0
Net Cash Flows from (Used for) Operating Activities	127.1	58.5
Investing Activities
Construction Expenditures	(571.8)	(390.4)
Change in Advances to Affiliates, Net	114.2	56.9
Payments to Acquire Property, Plant, and Equipment	(1.8)	(0.6)
Other Investing Activities	1.0	0.0
Net Cash Flows from (Used for) Investing Activities	(458.4)	(334.1)
Financing Activities
Capital Contributions from Parent	65.0	125.5
Change in Advances from Affiliates, Net	266.4	150.9
Other Financing Activities	(0.1)	(0.8)
Net Cash Flows from (Used for) Financing Activities	331.3	275.6
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
Net Cash Paid (Received) for Income Taxes	0.0	(0.6)
Construction Expenditures Included in Current Liabilities as of March 31,	210.6	189.2
Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	125.5	110.6
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	108.5	100.6
Deferred Income Taxes	11.0	52.2
Carrying Costs Income	(0.5)	(0.3)
Allowance for Equity Funds Used During Construction	(2.6)	(1.5)
Mark-to-Market of Risk Management Contracts	14.9	6.8
Deferred Fuel Over/Under-Recovery, Net	(90.7)	1.1
Change in Other Noncurrent Assets	3.9	1.0
Change in Other Noncurrent Liabilities	37.9	(3.7)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(14.2)	(2.2)
Fuel, Materials and Supplies	19.3	(6.9)
Accounts Payable	(21.6)	(12.7)
Accrued Taxes, Net	17.8	9.4
Other Current Assets	(15.8)	7.8
Other Current Liabilities	5.6	(3.5)
Net Cash Flows from (Used for) Operating Activities	199.5	259.0
Investing Activities
Construction Expenditures	(218.5)	(223.7)
Change in Advances to Affiliates, Net	0.0	0.4
Other Investing Activities	4.4	1.4
Net Cash Flows from (Used for) Investing Activities	(214.1)	(221.9)
Financing Activities
Change in Advances from Affiliates, Net	59.9	102.8
Retirement of Long-term Debt	(11.7)	(115.9)
Principal Payments for Capital Lease Obligations	(1.7)	(1.8)
Dividends Paid on Common Stock	(40.0)	(30.0)
Other Financing Activities	0.2	0.3
Net Cash Flows from (Used for) Financing Activities	6.7	(44.6)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(7.9)	(7.5)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	19.2	18.5
Cash and Cash Equivalents at Beginning of Period	2.9
Cash, Cash Equivalents and Restricted Cash at End of Period	11.3	11.0
Cash and Cash Equivalents at End of Period	1.2
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	23.4	23.8
Noncash Acquisitions Under Capital Leases	1.8	0.5
Construction Expenditures Included in Current Liabilities as of March 31,	94.5	63.7
Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	64.2	68.4
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	59.3	50.0
Deferred Income Taxes	13.7	48.8
Deferral of Incremental Nuclear Refueling Outage Expenses, Net	(12.3)	16.6
Carrying Costs Income	(2.4)	(3.4)
Allowance for Equity Funds Used During Construction	(1.8)	(2.1)
Mark-to-Market of Risk Management Contracts	3.4	2.3
Amortization of Nuclear Fuel	27.4	35.1
Deferred Fuel Over/Under-Recovery, Net	3.4	19.6
Change in Other Noncurrent Assets	(13.4)	(17.6)
Change in Other Noncurrent Liabilities	33.7	13.5
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	3.5	3.0
Fuel, Materials and Supplies	(4.5)	(8.5)
Accounts Payable	1.3	(22.5)
Accrued Taxes, Net	8.2	(6.9)
Other Current Assets	(11.1)	15.8
Other Current Liabilities	(27.8)	(41.2)
Net Cash Flows from (Used for) Operating Activities	147.2	174.3
Investing Activities
Construction Expenditures	(148.9)	(159.7)
Change in Advances to Affiliates, Net	(0.1)	0.0
Purchases of Investment Securities	(525.3)	(505.5)
Sales of Investment Securities	508.6	487.9
Acquisitions of Nuclear Fuel	(23.8)	(3.7)
Other Investing Activities	4.2	2.0
Net Cash Flows from (Used for) Investing Activities	(185.3)	(179.0)
Financing Activities
Issuance of Long-term Debt	0.0	76.7
Change in Advances from Affiliates, Net	102.5	71.6
Retirement of Long-term Debt	(29.4)	(109.5)
Principal Payments for Capital Lease Obligations	(2.7)	(2.9)
Dividends Paid on Common Stock	(33.5)	(31.3)
Other Financing Activities	0.5	0.1
Net Cash Flows from (Used for) Financing Activities	37.4	4.7
Net Increase (Decrease) in Cash and Cash Equivalents	(0.7)	0.0
Cash and Cash Equivalents at Beginning of Period	1.3	1.2
Cash and Cash Equivalents at End of Period	0.6	1.2
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	50.6	44.3
Net Cash Paid (Received) for Income Taxes	0.0	0.6
Noncash Acquisitions Under Capital Leases	1.7	1.5
Construction Expenditures Included in Current Liabilities as of March 31,	77.2	75.9
Acquisition of Nuclear Fuel Included in Current Liabilities as of March 31,	0.1	0.0
Expected Reimbursement For Spent Nuclear Fuel Dry Cask Storage	0.1	1.0
Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	79.6	86.2
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	64.8	57.3
Amortization Of Generation Deferrals	58.6	60.9
Deferred Income Taxes	(4.9)	36.7
Carrying Costs Income	(0.7)	(1.9)
Allowance for Equity Funds Used During Construction	(2.5)	(2.4)
Mark-to-Market of Risk Management Contracts	(33.7)	5.7
Property Taxes	62.9	58.4
Provision for Refund - Global Settlement	(5.4)	0.0
Change in Other Noncurrent Assets	14.3	(45.8)
Change in Other Noncurrent Liabilities	40.6	30.6
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	38.8	30.2
Fuel, Materials and Supplies	(1.9)	(1.8)
Accounts Payable	(22.5)	(34.9)
Accrued Taxes, Net	(92.8)	(107.2)
Other Current Assets	(7.5)	(0.3)
Other Current Liabilities	(2.9)	(31.2)
Net Cash Flows from (Used for) Operating Activities	184.8	140.5
Investing Activities
Construction Expenditures	(168.2)	(108.4)
Change in Advances to Affiliates, Net	(200.4)	24.2
Other Investing Activities	1.7	2.0
Net Cash Flows from (Used for) Investing Activities	(366.9)	(82.2)
Financing Activities
Issuance of Long-term Debt	393.3	0.0
Change in Advances from Affiliates, Net	(87.8)	18.3
Retirement of Long-term Debt	(22.9)	(22.5)
Principal Payments for Capital Lease Obligations	(0.9)	(1.0)
Dividends Paid on Common Stock	(112.5)	(65.0)
Other Financing Activities	0.5	0.6
Net Cash Flows from (Used for) Financing Activities	169.7	(69.6)
Net Increase (Decrease) in Cash, Cash Equivalents and Restricted Cash	(12.4)	(11.3)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	29.7	30.3
Cash and Cash Equivalents at Beginning of Period	3.1
Cash, Cash Equivalents and Restricted Cash at End of Period	17.3	19.0
Cash and Cash Equivalents at End of Period	1.4
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	17.0	17.2
Net Cash Paid (Received) for Income Taxes	0.0	1.7
Noncash Acquisitions Under Capital Leases	1.4	1.3
Construction Expenditures Included in Current Liabilities as of March 31,	52.3	28.3
Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	(7.2)	4.8
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	36.8	33.5
Deferred Income Taxes	(4.5)	27.4
Allowance for Equity Funds Used During Construction	0.1	(0.4)
Mark-to-Market of Risk Management Contracts	3.5	0.3
Property Taxes	(30.1)	(29.8)
Deferred Fuel Over/Under-Recovery, Net	14.6	(13.1)
Change in Other Noncurrent Assets	0.0	(9.3)
Change in Other Noncurrent Liabilities	5.7	(1.9)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	6.9	16.6
Fuel, Materials and Supplies	(1.7)	3.4
Accounts Payable	(10.9)	(27.7)
Accrued Taxes, Net	22.4	(0.3)
Other Current Assets	0.9	0.3
Other Current Liabilities	(1.3)	(22.3)
Net Cash Flows from (Used for) Operating Activities	35.2	(18.5)
Investing Activities
Construction Expenditures	(54.4)	(75.7)
Other Investing Activities	2.0	0.9
Net Cash Flows from (Used for) Investing Activities	(52.4)	(74.8)
Financing Activities
Change in Advances from Affiliates, Net	29.5	111.7
Retirement of Long-term Debt	(0.1)	(0.1)
Principal Payments for Capital Lease Obligations	(1.0)	(1.1)
Dividends Paid on Common Stock	(12.5)	(17.5)
Other Financing Activities	0.3	0.1
Net Cash Flows from (Used for) Financing Activities	16.2	93.1
Net Increase (Decrease) in Cash and Cash Equivalents	(1.0)	(0.2)
Cash and Cash Equivalents at Beginning of Period	1.6	1.5
Cash and Cash Equivalents at End of Period	0.6	1.3
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	10.3	15.9
Net Cash Paid (Received) for Income Taxes	0.0	(2.6)
Noncash Acquisitions Under Capital Leases	0.9	0.7
Construction Expenditures Included in Current Liabilities as of March 31,	25.4	22.3
Southwestern Electric Power Co [Member]
Operating Activities
Net Income (Loss)	13.4	17.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	57.4	50.8
Deferred Income Taxes	1.0	43.1
Allowance for Equity Funds Used During Construction	(2.3)	(0.8)
Mark-to-Market of Risk Management Contracts	5.1	0.4
Property Taxes	(48.8)	(45.3)
Deferred Fuel Over/Under-Recovery, Net	(4.6)	(3.4)
Change in Other Noncurrent Assets	1.3	(0.6)
Change in Other Noncurrent Liabilities	18.8	(12.1)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	27.9	23.1
Fuel, Materials and Supplies	2.2	12.5
Accounts Payable	(24.6)	(33.5)
Accrued Taxes, Net	55.2	11.8
Accrued Interest	(13.0)	(20.3)
Other Current Assets	(0.8)	3.2
Other Current Liabilities	(12.5)	(19.1)
Net Cash Flows from (Used for) Operating Activities	75.7	27.1
Investing Activities
Construction Expenditures	(139.7)	(75.6)
Change in Advances to Affiliates, Net	0.0	167.8
Other Investing Activities	(5.4)	(4.4)
Net Cash Flows from (Used for) Investing Activities	(145.1)	87.8
Financing Activities
Issuance of Long-term Debt	444.6	0.0
Change in Short-term Debt, Net	0.6	0.0
Change in Advances from Affiliates, Net	29.9	167.9
Retirement of Long-term Debt	(383.4)	(251.7)
Principal Payments for Capital Lease Obligations	(2.8)	(2.8)
Dividends Paid on Common Stock	(20.0)	(27.5)
Dividends Paid on Common Stock	(0.8)	(1.1)
Other Financing Activities	0.4	0.3
Net Cash Flows from (Used for) Financing Activities	68.5	(114.9)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.9)	0.0
Cash and Cash Equivalents at Beginning of Period	1.6	10.3
Cash and Cash Equivalents at End of Period	0.7	10.3
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	43.7	50.6
Net Cash Paid (Received) for Income Taxes	(0.1)	0.0
Noncash Acquisitions Under Capital Leases	1.9	1.3
Construction Expenditures Included in Current Liabilities as of March 31,	$ 50.3	$ 31.8