Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities
Net Income (Loss)	$ 594.2	$ 503.1
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	481.9	497.1
Deferred Income Taxes	136.2	330.2
Other Asset Impairment Charges	11.2	0.0
Carrying Costs Income	(5.9)	(3.9)
Allowance for Equity Funds Used During Construction	(21.2)	(31.7)
Mark-to-Market of Risk Management Contracts	6.0	20.9
Amortization of Nuclear Fuel	35.1	40.5
Property Taxes	(44.4)	(34.4)
Deferred Fuel Over/Under-Recovery, Net	19.3	10.6
Gain on Sale of Merchant Generation Assets	(226.5)	0.0
Recovery of Ohio Capacity Costs	30.2	35.1
Change in Other Noncurrent Assets	(104.4)	(68.3)
Change in Other Noncurrent Liabilities	45.0	1.8
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	235.8	(10.8)
Fuel, Materials and Supplies	13.4	(95.4)
Accounts Payable	(250.7)	(34.4)
Accrued Taxes, Net	186.8	(169.2)
Other Current Assets	(45.9)	21.6
Other Current Liabilities	(289.3)	(212.9)
Net Cash Flows from (Used for) Operating Activities	806.8	799.9
Investing Activities
Construction Expenditures	(1,365.8)	(1,203.5)
Change in Other Temporary Investments, Net	55.6	122.8
Purchases of Investment Securities	(506.0)	(1,152.0)
Sales of Investment Securities	487.9	1,137.7
Acquisitions of Nuclear Fuel	(3.7)	(45.5)
Proceeds from Sale of Merchant Generation Assets	2,159.6	0.0
Other Investing Activities	17.2	2.2
Net Cash Flows from (Used for) Investing Activities	844.8	(1,138.3)
Financing Activities
Issuance of Common Stock, Net	0.0	12.1
Issuance of Long-term Debt	82.9	525.1
Change in Short-term Debt, Net	(177.0)	421.0
Retirement of Long-term Debt	(1,242.3)	(322.4)
Make Whole Premium on Extinguishment of Long-term Debt	(44.9)	0.0
Principal Payments for Capital Lease Obligations	(16.6)	(24.9)
Dividends Paid on Common Stock	(291.4)	(276.5)
Other Financing Activities	2.2	18.0
Net Cash Flows from (Used for) Financing Activities	(1,687.1)	352.4
Net Increase (Decrease) in Cash and Cash Equivalents	(35.5)	14.0
Cash and Cash Equivalents at Beginning of Period	210.5	176.4
Cash and Cash Equivalents at End of Period	175.0	190.4
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	205.9	199.0
Net Cash Paid (Received) for Income Taxes	(88.8)	7.3
Noncash Acquisitions Under Capital Leases	11.4	45.4
Construction Expenditures Included in Current Liabilities as of March 31,	515.6	544.3
Acquisition of Nuclear Fuel Included in Current Liabilities as of March 31,	0.0	29.1
Expected Reimbursement For Spent Nuclear Fuel Dry Cask Storage	1.0	0.0
Appalachian Power Co [Member]
Operating Activities
Net Income (Loss)	110.6	126.3
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	100.6	95.5
Deferred Income Taxes	52.2	30.9
Allowance for Equity Funds Used During Construction	(1.5)	(2.3)
Mark-to-Market of Risk Management Contracts	6.8	9.1
Deferred Fuel Over/Under-Recovery, Net	1.1	5.1
Change in Other Noncurrent Assets	1.0	17.7
Change in Other Noncurrent Liabilities	(3.7)	(9.0)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	(2.2)	(26.1)
Fuel, Materials and Supplies	(6.9)	(28.3)
Accounts Payable	(12.7)	(2.9)
Accrued Taxes, Net	9.4	54.5
Other Current Assets	7.8	(4.1)
Other Current Liabilities	(3.5)	(8.4)
Net Cash Flows from (Used for) Operating Activities	259.0	258.0
Investing Activities
Construction Expenditures	(223.7)	(168.9)
Change in Restricted Cash for Securitized Funding	7.8	7.3
Change in Advances to Affiliates, Net	0.4	0.8
Other Investing Activities	1.4	4.1
Net Cash Flows from (Used for) Investing Activities	(214.1)	(156.7)
Financing Activities
Issuance of Long-term Debt	0.0	124.8
Change in Advances from Affiliates, Net	102.8	(9.8)
Retirement of Long-term Debt	(115.9)	(136.5)
Principal Payments for Capital Lease Obligations	(1.8)	(1.5)
Dividends Paid on Common Stock	(30.0)	(75.0)
Other Financing Activities	0.3	0.3
Net Cash Flows from (Used for) Financing Activities	(44.6)	(97.7)
Net Increase (Decrease) in Cash and Cash Equivalents	0.3	3.6
Cash and Cash Equivalents at Beginning of Period	2.7	2.8
Cash and Cash Equivalents at End of Period	3.0	6.4
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	23.8	23.1
Net Cash Paid (Received) for Income Taxes	0.0	(17.9)
Noncash Acquisitions Under Capital Leases	0.5	0.7
Construction Expenditures Included in Current Liabilities as of March 31,	63.7	70.4
Indiana Michigan Power Co [Member]
Operating Activities
Net Income (Loss)	68.4	74.7
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	50.0	47.1
Deferred Income Taxes	48.8	44.0
Deferral of Incremental Nuclear Refueling Outage Expenses, Net	16.6	(8.4)
Allowance for Equity Funds Used During Construction	(2.1)	(2.3)
Mark-to-Market of Risk Management Contracts	2.3	2.4
Amortization of Nuclear Fuel	35.1	40.5
Deferred Fuel Over/Under-Recovery, Net	19.6	3.8
Change in Other Noncurrent Assets	(17.6)	(4.8)
Change in Other Noncurrent Liabilities	13.5	9.1
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	3.0	(2.0)
Fuel, Materials and Supplies	(8.5)	(16.0)
Accounts Payable	(22.5)	(9.9)
Accrued Taxes, Net	(6.9)	2.5
Other Current Assets	15.8	6.1
Other Current Liabilities	(41.2)	(32.5)
Net Cash Flows from (Used for) Operating Activities	174.3	154.3
Investing Activities
Construction Expenditures	(159.7)	(136.4)
Change in Advances to Affiliates, Net	0.0	(0.6)
Purchases of Investment Securities	(505.5)	(1,151.6)
Sales of Investment Securities	487.9	1,137.7
Acquisitions of Nuclear Fuel	(3.7)	(45.5)
Other Investing Activities	2.0	3.3
Net Cash Flows from (Used for) Investing Activities	(179.0)	(193.1)
Financing Activities
Issuance of Long-term Debt	76.7	394.8
Change in Advances from Affiliates, Net	71.6	(284.8)
Retirement of Long-term Debt	(109.5)	(28.8)
Principal Payments for Capital Lease Obligations	(2.9)	(9.6)
Dividends Paid on Common Stock	(31.3)	(31.3)
Other Financing Activities	0.1	0.7
Net Cash Flows from (Used for) Financing Activities	4.7	41.0
Net Increase (Decrease) in Cash and Cash Equivalents	0.0	2.2
Cash and Cash Equivalents at Beginning of Period	1.2	1.1
Cash and Cash Equivalents at End of Period	1.2	3.3
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	44.3	35.2
Net Cash Paid (Received) for Income Taxes	0.6	(4.9)
Noncash Acquisitions Under Capital Leases	1.5	14.9
Construction Expenditures Included in Current Liabilities as of March 31,	75.9	68.4
Acquisition of Nuclear Fuel Included in Current Liabilities as of March 31,	0.0	29.1
Expected Reimbursement For Spent Nuclear Fuel Dry Cask Storage	1.0	0.0
Ohio Power Co [Member]
Operating Activities
Net Income (Loss)	86.2	70.2
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	57.3	61.3
Amortization Of Generation Deferrals	60.9	55.1
Deferred Income Taxes	36.7	7.3
Carrying Costs Income	(1.9)	(1.9)
Allowance for Equity Funds Used During Construction	(2.4)	(1.7)
Mark-to-Market of Risk Management Contracts	5.7	26.9
Property Taxes	58.4	56.0
Change in Other Noncurrent Assets	(45.8)	(16.2)
Change in Other Noncurrent Liabilities	30.6	6.5
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	30.2	(4.7)
Fuel, Materials and Supplies	(1.8)	(3.0)
Accounts Payable	(34.9)	(30.4)
Customer Deposits	0.9	24.0
Accrued Taxes, Net	(107.2)	(148.4)
Other Current Assets	(0.3)	(0.4)
Other Current Liabilities	(32.1)	(20.7)
Net Cash Flows from (Used for) Operating Activities	140.5	79.9
Investing Activities
Construction Expenditures	(108.4)	(99.2)
Change in Restricted Cash for Securitized Funding	11.2	11.5
Change in Advances to Affiliates, Net	24.2	109.2
Other Investing Activities	2.0	3.1
Net Cash Flows from (Used for) Investing Activities	(71.0)	24.6
Financing Activities
Change in Advances from Affiliates, Net	18.3	0.0
Retirement of Long-term Debt	(22.5)	(22.8)
Principal Payments for Capital Lease Obligations	(1.0)	(1.0)
Dividends Paid on Common Stock	(65.0)	(75.0)
Other Financing Activities	0.6	0.5
Net Cash Flows from (Used for) Financing Activities	(69.6)	(98.3)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.1)	6.2
Cash and Cash Equivalents at Beginning of Period	3.1	3.1
Cash and Cash Equivalents at End of Period	3.0	9.3
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	17.2	17.8
Net Cash Paid (Received) for Income Taxes	1.7	72.5
Noncash Acquisitions Under Capital Leases	1.3	0.8
Construction Expenditures Included in Current Liabilities as of March 31,	28.3	23.1
Public Service Co Of Oklahoma [Member]
Operating Activities
Net Income (Loss)	4.8	15.7
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	33.5	35.3
Deferred Income Taxes	27.4	30.5
Allowance for Equity Funds Used During Construction	(0.4)	(2.3)
Mark-to-Market of Risk Management Contracts	0.3	0.0
Property Taxes	(29.8)	(24.1)
Deferred Fuel Over/Under-Recovery, Net	(13.1)	(8.3)
Customer Refund Liability, Current	(11.4)	6.7
Change in Regulatory Assets	(6.7)	(3.9)
Change in Regulatory Liabilities	(0.4)	(1.1)
Change in Other Noncurrent Assets	(2.6)	(6.3)
Change in Other Noncurrent Liabilities	(1.5)	(0.4)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	16.6	5.0
Fuel, Materials and Supplies	3.4	(3.5)
Accounts Payable	(27.7)	(17.6)
Accrued Taxes, Net	(0.3)	17.6
Other Current Assets	0.3	(0.2)
Other Current Liabilities	(10.9)	(10.7)
Net Cash Flows from (Used for) Operating Activities	(18.5)	32.4
Investing Activities
Construction Expenditures	(75.7)	(104.1)
Change in Advances to Affiliates, Net	0.0	72.2
Other Investing Activities	0.9	2.1
Net Cash Flows from (Used for) Investing Activities	(74.8)	(29.8)
Financing Activities
Change in Advances from Affiliates, Net	111.7	0.0
Retirement of Long-term Debt	(0.1)	(0.1)
Principal Payments for Capital Lease Obligations	(1.1)	(1.0)
Dividends Paid on Common Stock	(17.5)	0.0
Other Financing Activities	0.1	0.3
Net Cash Flows from (Used for) Financing Activities	93.1	(0.8)
Net Increase (Decrease) in Cash and Cash Equivalents	(0.2)	1.8
Cash and Cash Equivalents at Beginning of Period	1.5	1.4
Cash and Cash Equivalents at End of Period	1.3	3.2
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	15.9	15.1
Net Cash Paid (Received) for Income Taxes	(2.6)	(23.2)
Noncash Acquisitions Under Capital Leases	0.7	1.4
Construction Expenditures Included in Current Liabilities as of March 31,	22.3	35.7
Southwestern Electric Power Co [Member]
Operating Activities
Net Income (Loss)	17.3	24.5
Adjustments to Reconcile Net Income to Net Cash Flows from (Used for) Operating Activities:
Depreciation and Amortization	50.8	47.5
Deferred Income Taxes	43.1	44.6
Allowance for Equity Funds Used During Construction	(0.8)	(7.4)
Mark-to-Market of Risk Management Contracts	0.4	0.1
Property Taxes	(45.3)	(41.4)
Deferred Fuel Over/Under-Recovery, Net	(3.4)	3.7
Change in Other Noncurrent Assets	(0.6)	5.3
Change in Other Noncurrent Liabilities	(12.1)	(1.9)
Changes in Certain Components of Working Capital:
Accounts Receivable, Net	23.1	2.6
Fuel, Materials and Supplies	12.5	13.7
Accounts Payable	(33.5)	(19.9)
Accrued Taxes, Net	11.8	(13.2)
Accrued Interest	(20.3)	(20.8)
Other Current Assets	3.2	(1.7)
Other Current Liabilities	(19.1)	(28.2)
Net Cash Flows from (Used for) Operating Activities	27.1	7.5
Investing Activities
Construction Expenditures	(75.6)	(116.6)
Change in Advances to Affiliates, Net	167.8	0.0
Other Investing Activities	(4.4)	(7.0)
Net Cash Flows from (Used for) Investing Activities	87.8	(123.6)
Financing Activities
Change in Advances from Affiliates, Net	167.9	159.5
Retirement of Long-term Debt	(251.7)	(1.6)
Principal Payments for Capital Lease Obligations	(2.8)	(4.5)
Dividends Paid on Common Stock	(27.5)	(30.0)
Dividends Paid on Common Stock	(1.1)	(1.2)
Other Financing Activities	0.3	1.0
Net Cash Flows from (Used for) Financing Activities	(114.9)	123.2
Net Increase (Decrease) in Cash and Cash Equivalents	0.0	7.1
Cash and Cash Equivalents at Beginning of Period	10.3	5.2
Cash and Cash Equivalents at End of Period	10.3	12.3
Supplementary Information
Cash Paid for Interest, Net of Capitalized Amounts	50.6	47.7
Net Cash Paid (Received) for Income Taxes	0.0	14.0
Noncash Acquisitions Under Capital Leases	1.3	4.9
Construction Expenditures Included in Current Liabilities as of March 31,	$ 31.8	$ 83.7