Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities
Net Income (Loss)	$ 1,527.1	$ 242.8
Income (Loss) from Discontinued Operations	0.0	(2.5)
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	1,527.1	245.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	1,485.9	1,550.2
Deferred Income Taxes	740.9	(47.0)
Asset Impairments and Other Related Charges	10.6	2,264.9
Carrying Costs Income	(14.2)	(11.9)
Allowance for Equity Funds Used During Construction	(62.2)	(86.1)
Mark-to-Market of Risk Management Contracts	(56.2)	56.6
Amortization of Nuclear Fuel	104.8	109.7
Pension Contributions to Qualified Plan Trust	(93.3)	(84.8)
Property Taxes	291.4	288.3
Deferred Fuel Over/Under-Recovery, Net	81.0	(28.5)
Gain on Sale of Merchant Generation Assets	(226.4)	0.0
Gain on Sale of Equity Investment	(12.4)	0.0
Recovery of Ohio Capacity Costs, Net	65.6	108.8
Provision for Refund - Global Settlement	(93.3)	0.0
Change in Other Noncurrent Assets	(345.2)	(243.4)
Change in Other Noncurrent Liabilities	205.7	41.3
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	201.3	(240.8)
Fuel, Materials and Supplies	58.5	11.6
Accounts Payable	(91.0)	47.8
Accrued Taxes, Net	(310.1)	(393.0)
Other Current Assets	(98.2)	31.5
Other Current Liabilities	(260.3)	(211.4)
Net Cash Flows from (Used for) Operating Activities	3,124.2	3,421.0
Investing Activities
Construction Expenditures	(3,778.2)	(3,387.0)
Change In Other Temporary Investments, Net	34.5	109.2
Purchases of Investment Securities	(1,855.8)	(2,454.5)
Sales of Investment Securities	1,808.6	2,427.0
Acquisitions of Nuclear Fuel	(73.2)	(127.6)
Proceeds From Sale Of Merchant Generation Assets	2,159.6	0.0
Other Investing Activities	27.9	4.2
Net Cash Flows from (Used for) Continuing Investing Activities	(1,676.6)	(3,428.7)
Financing Activities
Issuance of Common Stock, Net	0.0	34.2
Issuance of Long-term Debt	2,742.7	1,559.6
Change in Short-term Debt, Net	(653.7)	678.3
Retirement of Long-term Debt	(2,427.2)	(1,307.6)
Make Whole Premium on Extinguishment of Long-term Debt	(46.1)	0.0
Principal Payments for Capital Lease Obligations	(50.5)	(81.9)
Dividends Paid on Common Stock	(875.0)	(829.8)
Other Financing Activities	(4.4)	(6.8)
Net Cash Flows from (Used for) Financing Activities	(1,314.2)	46.0
Cash Flows from Discontinued Operations
Operating Activities	0.0	(2.5)
Investing Activities	0.0	0.0
Financing Activities	0.0	0.0
Net Increase (Decrease) in Cash and Cash Equivalents	133.4	35.8
Cash and Cash Equivalents at Beginning of Period	210.5	176.4
Cash and Cash Equivalents at End of Period	343.9	212.2
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	613.8	637.0
Net Cash Paid (Received) for Income Taxes	(6.8)	32.2
Noncash Acquisitions Under Capital Leases	44.5	65.8
Construction Expenditures Included in Current Liabilities as of September 30,	791.6	604.8
Construction Expenditures Included in Noncurrent Liabilities as of September 30,	71.8	0.0
Acquisition of Nuclear Fuel Included in Current Liabilities as of September 30,	0.6	0.3
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	2.8	0.0
AEP Transmission Co [Member]
Operating Activities
Net Income (Loss)	224.3	153.0
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	70.9	47.5
Deferred Income Taxes	193.0	161.2
Allowance for Equity Funds Used During Construction	(36.0)	(39.7)
Property Taxes	72.4	63.5
Long-term Accounts Receivable - Affiliated	(13.8)	0.0
Change in Other Noncurrent Assets	7.6	(6.4)
Change in Other Noncurrent Liabilities	25.7	0.6
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(44.4)	(43.3)
Fuel, Materials and Supplies	(11.0)	(1.5)
Accounts Payable	8.6	(1.7)
Accrued Taxes, Net	(66.0)	61.2
Accrued Interest	18.4	11.3
Other Current Assets	(5.3)	(0.1)
Other Current Liabilities	0.5	0.1
Net Cash Flows from (Used for) Operating Activities	444.9	405.7
Investing Activities
Construction Expenditures	(1,050.7)	(799.8)
Change in Advances to Affiliates, Net	(223.8)	83.7
Other Investing Activities	(2.9)	(4.6)
Net Cash Flows from (Used for) Investing Activities	(1,277.4)	(720.7)
Financing Activities
Capital Contributions from Member	185.5	116.0
Issuance of Long-term Debt	618.3	0.0
Change in Advances from Affiliates, Net	28.7	199.0
Net Cash Flows from (Used for) Financing Activities	832.5	315.0
Cash Flows from Discontinued Operations
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	28.6	20.0
Net Cash Paid (Received) for Income Taxes	(93.4)	(209.8)
Construction Expenditures Included in Current Liabilities as of September 30,	239.0	204.8
Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	248.7	303.8
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	304.1	290.0
Deferred Income Taxes	121.7	100.9
Carrying Costs Income	(1.0)	(0.2)
Allowance for Equity Funds Used During Construction	(6.2)	(9.1)
Mark-to-Market of Risk Management Contracts	(28.3)	18.4
Pension Contributions to Qualified Plan Trust	(10.2)	(8.8)
Property Taxes	29.8	29.2
Deferred Fuel Over/Under-Recovery, Net	4.9	19.0
Change in Other Noncurrent Assets	8.3	(5.1)
Change in Other Noncurrent Liabilities	7.9	(23.0)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	39.9	(20.5)
Fuel, Materials and Supplies	14.0	(1.2)
Accounts Payable	6.2	4.9
Accrued Taxes, Net	(44.2)	(13.9)
Other Current Assets	(2.5)	(0.2)
Other Current Liabilities	9.1	(4.1)
Net Cash Flows from (Used for) Operating Activities	702.2	680.1
Investing Activities
Construction Expenditures	(560.0)	(472.7)
Change in Restricted Cash for Securitized Funding	7.5	7.0
Change in Advances to Affiliates, Net	0.5	1.2
Other Investing Activities	11.8	10.6
Net Cash Flows from (Used for) Investing Activities	(540.2)	(453.9)
Financing Activities
Issuance of Long-term Debt	320.9	314.1
Change in Advances from Affiliates, Net	(10.1)	(96.9)
Retirement of Long-term Debt	(377.9)	(213.6)
Principal Payments for Capital Lease Obligations	(5.2)	(4.7)
Dividends Paid on Common Stock	(90.0)	(225.0)
Other Financing Activities	0.5	0.4
Net Cash Flows from (Used for) Financing Activities	(161.8)	(225.7)
Cash Flows from Discontinued Operations
Net Increase (Decrease) in Cash and Cash Equivalents	0.2	0.5
Cash and Cash Equivalents at Beginning of Period	2.7	2.8
Cash and Cash Equivalents at End of Period	2.9	3.3
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	107.1	113.2
Net Cash Paid (Received) for Income Taxes	24.4	55.8
Noncash Acquisitions Under Capital Leases	2.9	2.1
Construction Expenditures Included in Current Liabilities as of September 30,	107.2	66.8
Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	143.8	201.4
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	154.8	143.2
Deferred Income Taxes	132.2	116.2
Deferral of Incremental Nuclear Refueling Outage Expenses, Net	15.5	(17.4)
Asset Impairments and Other Related Charges	0.0	10.5
Allowance for Equity Funds Used During Construction	(8.1)	(10.9)
Mark-to-Market of Risk Management Contracts	(7.5)	0.5
Amortization of Nuclear Fuel	104.8	109.7
Pension Contributions to Qualified Plan Trust	(13.0)	(12.7)
Deferred Fuel Over/Under-Recovery, Net	22.0	6.1
Change in Other Noncurrent Assets	(42.1)	0.0
Change in Other Noncurrent Liabilities	40.9	30.0
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	19.3	17.0
Fuel, Materials and Supplies	(4.1)	(1.1)
Accounts Payable	16.6	(17.9)
Accrued Taxes, Net	(30.2)	(16.5)
Other Current Assets	8.0	6.7
Other Current Liabilities	(28.6)	(27.8)
Net Cash Flows from (Used for) Operating Activities	524.3	537.0
Investing Activities
Construction Expenditures	(469.2)	(405.1)
Change in Advances to Affiliates, Net	(0.1)	(0.7)
Purchases of Investment Securities	(1,842.2)	(2,452.9)
Sales of Investment Securities	1,808.6	2,427.0
Acquisitions of Nuclear Fuel	(73.2)	(127.6)
Other Investing Activities	7.3	7.8
Net Cash Flows from (Used for) Investing Activities	(568.8)	(551.5)
Financing Activities
Issuance of Long-term Debt	411.1	482.7
Change in Advances from Affiliates, Net	(37.7)	(268.0)
Retirement of Long-term Debt	(227.1)	(76.8)
Principal Payments for Capital Lease Obligations	(8.7)	(29.8)
Dividends Paid on Common Stock	(93.7)	(93.8)
Other Financing Activities	0.7	0.7
Net Cash Flows from (Used for) Financing Activities	44.6	15.0
Cash Flows from Discontinued Operations
Net Increase (Decrease) in Cash and Cash Equivalents	0.1	0.5
Cash and Cash Equivalents at Beginning of Period	1.2	1.1
Cash and Cash Equivalents at End of Period	1.3	1.6
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	92.0	85.6
Net Cash Paid (Received) for Income Taxes	(69.6)	(36.0)
Noncash Acquisitions Under Capital Leases	5.9	16.8
Construction Expenditures Included in Current Liabilities as of September 30,	74.5	83.4
Acquisition of Nuclear Fuel Included in Current Liabilities as of September 30,	0.6	0.3
Expected Reimbursement for Spent Nuclear Fuel Dry Cask Storage	2.8	0.1
Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	231.1	244.7
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	165.7	189.0
Amortization Of Generation Deferrals	172.9	173.0
Deferred Income Taxes	117.5	28.6
Carrying Costs Income	(3.0)	(4.0)
Allowance for Equity Funds Used During Construction	(4.1)	(3.7)
Mark-to-Market of Risk Management Contracts	19.5	124.7
Pension Contributions to Qualified Plan Trust	(8.2)	(7.1)
Property Taxes	175.9	169.1
Provision for Refund - Global Settlement	(93.3)	0.0
Change in Other Noncurrent Assets	(126.7)	(124.9)
Change in Other Noncurrent Liabilities	43.4	17.2
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	14.9	8.8
Fuel, Materials and Supplies	(7.1)	0.5
Accounts Payable	(31.2)	2.0
Accrued Taxes, Net	(284.3)	(291.1)
Other Current Assets	(17.3)	(5.7)
Other Current Liabilities	(34.8)	(46.8)
Net Cash Flows from (Used for) Operating Activities	330.9	474.3
Investing Activities
Construction Expenditures	(362.5)	(276.4)
Change in Restricted Cash for Securitized Funding	11.6	11.6
Change in Advances to Affiliates, Net	24.2	330.9
Other Investing Activities	6.9	9.0
Net Cash Flows from (Used for) Investing Activities	(319.8)	75.1
Financing Activities
Change in Advances from Affiliates, Net	167.6	0.0
Retirement of Long-term Debt	(46.4)	(395.9)
Principal Payments for Capital Lease Obligations	(3.1)	(3.1)
Dividends Paid on Common Stock	(130.0)	(150.0)
Other Financing Activities	0.8	0.5
Net Cash Flows from (Used for) Financing Activities	(11.1)	(548.5)
Cash Flows from Discontinued Operations
Net Increase (Decrease) in Cash and Cash Equivalents	0.0	0.9
Cash and Cash Equivalents at Beginning of Period	3.1	3.1
Cash and Cash Equivalents at End of Period	3.1	4.0
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	68.1	78.2
Net Cash Paid (Received) for Income Taxes	69.6	178.0
Noncash Acquisitions Under Capital Leases	3.6	2.4
Construction Expenditures Included in Current Liabilities as of September 30,	56.8	30.0
Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	71.4	97.4
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	97.8	109.9
Deferred Income Taxes	93.7	79.5
Allowance for Equity Funds Used During Construction	(0.4)	(4.9)
Mark-to-Market of Risk Management Contracts	(3.9)	(0.7)
Pension Contributions to Qualified Plan Trust	(5.3)	(5.6)
Property Taxes	(9.4)	(8.0)
Deferred Fuel Over/Under-Recovery, Net	(5.6)	(80.2)
Provision for Refund	(39.4)	13.8
Change in Other Noncurrent Assets	(19.8)	(18.8)
Change in Other Noncurrent Liabilities	(1.4)	(3.7)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	5.8	4.4
Fuel, Materials and Supplies	13.5	(2.4)
Accounts Payable	(18.5)	23.1
Accrued Taxes, Net	20.1	45.4
Other Current Assets	(8.2)	(2.2)
Other Current Liabilities	1.5	(14.9)
Net Cash Flows from (Used for) Operating Activities	191.9	232.1
Investing Activities
Construction Expenditures	(203.1)	(266.8)
Change in Advances to Affiliates, Net	0.0	29.5
Other Investing Activities	1.5	8.7
Net Cash Flows from (Used for) Investing Activities	(201.6)	(228.6)
Financing Activities
Issuance of Long-term Debt	0.0	150.0
Change in Advances from Affiliates, Net	66.0	0.0
Retirement of Long-term Debt	(0.3)	(150.3)
Principal Payments for Capital Lease Obligations	(3.2)	(3.0)
Dividends Paid on Common Stock	(52.5)	0.0
Other Financing Activities	0.3	0.4
Net Cash Flows from (Used for) Financing Activities	10.3	(2.9)
Cash Flows from Discontinued Operations
Net Increase (Decrease) in Cash and Cash Equivalents	0.6	0.6
Cash and Cash Equivalents at Beginning of Period	1.5	1.4
Cash and Cash Equivalents at End of Period	2.1	2.0
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	40.9	45.0
Net Cash Paid (Received) for Income Taxes	(46.6)	(50.3)
Noncash Acquisitions Under Capital Leases	1.0	2.2
Construction Expenditures Included in Current Liabilities as of September 30,	15.1	20.2
Southwestern Electric Power Co [Member]
Operating Activities
Net Income (Loss)	126.5	153.2
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	158.1	148.1
Deferred Income Taxes	79.8	141.9
Allowance for Equity Funds Used During Construction	(1.2)	(9.5)
Mark-to-Market of Risk Management Contracts	(12.5)	(5.8)
Pension Contributions to Qualified Plan Trust	(8.9)	(8.3)
Property Taxes	(15.4)	(13.7)
Deferred Fuel Over/Under-Recovery, Net	2.4	1.2
Change in Other Noncurrent Assets	(2.9)	18.4
Change in Other Noncurrent Liabilities	(5.2)	(25.8)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	12.1	12.2
Fuel, Materials and Supplies	13.6	33.4
Accounts Payable	(25.7)	(17.2)
Accrued Taxes, Net	69.1	14.1
Accrued Interest	(20.0)	(20.0)
Other Current Assets	0.7	(2.4)
Other Current Liabilities	(14.6)	(24.8)
Net Cash Flows from (Used for) Operating Activities	355.9	395.0
Investing Activities
Construction Expenditures	(265.3)	(315.3)
Change in Advances to Affiliates, Net	167.8	(297.4)
Other Investing Activities	3.1	(1.9)
Net Cash Flows from (Used for) Investing Activities	(94.4)	(614.6)
Financing Activities
Issuance of Long-term Debt	114.6	402.2
Change in Short-term Debt, Net	14.3	0.0
Change in Advances from Affiliates, Net	48.3	(58.3)
Retirement of Long-term Debt	(353.6)	(3.3)
Principal Payments for Capital Lease Obligations	(8.4)	(18.6)
Dividends Paid on Common Stock	(82.5)	(90.0)
Dividends Paid on Common Stock	(2.7)	(3.5)
Other Financing Activities	0.4	1.1
Net Cash Flows from (Used for) Financing Activities	(269.6)	229.6
Cash Flows from Discontinued Operations
Net Increase (Decrease) in Cash and Cash Equivalents	(8.1)	10.0
Cash and Cash Equivalents at Beginning of Period	10.3	5.2
Cash and Cash Equivalents at End of Period	2.2	15.2
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	109.4	107.6
Net Cash Paid (Received) for Income Taxes	(70.5)	(66.6)
Noncash Acquisitions Under Capital Leases	2.8	5.5
Construction Expenditures Included in Current Liabilities as of September 30,	$ 40.7	$ 54.3