Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Current Assets
Cash and Cash Equivalents	$ 211.2	$ 214.6
Restricted Cash	176.1	198.0
Other Temporary Investments	163.1	161.7
Fuel	352.8	387.7
Property, Plant and Equipment
Other Property, Plant and Equipment	3,880.8	3,706.3
Accumulated Depreciation and Amortization	17,571.4	17,167.0
Other Noncurrent Assets
Securitized Transition Assets	1,082.1	1,211.2
Current Liabilities
Long-term Debt Due Within One Year	2,281.4	1,753.7
Accrued Interest	235.2	234.5
Noncurrent Liabilities
Long-term Debt	$ 19,750.6	$ 19,419.6
Equity
Common Stock, Par Value Per Share	$ 6.50	$ 6.50
Common Stock, Shares Authorized	600,000,000	600,000,000
Common Stock, Shares, Issued	513,130,857	512,210,644
Treasury Stock, Shares	20,204,160	20,205,046
AEP Subsidiaries [Member]
Current Assets
Restricted Cash	$ 176.1	$ 198.0
Other Temporary Investments	157.1	155.4
Current Liabilities
Long-term Debt Due Within One Year	423.2	406.9
Noncurrent Liabilities
Long-term Debt	1,247.3	1,410.5
AEP Texas Inc. [Member]
Current Assets
Cash and Cash Equivalents	0.1	2.0
Restricted Cash	131.9	155.2
Fuel	4.6	3.6
Property, Plant and Equipment
Other Property, Plant and Equipment	488.9	461.0
Accumulated Depreciation and Amortization	1,627.8	1,594.5
Other Noncurrent Assets
Securitized Transition Assets	786.6	891.2
Current Liabilities
Long-term Debt Due Within One Year	293.7	266.1
Accrued Interest	41.5	42.2
Noncurrent Liabilities
Long-term Debt	3,697.6	3,383.2
AEP Texas Inc. [Member] | AEP Texas Central Transition Funding Co [Member]
Other Noncurrent Assets
Securitized Transition Assets	769.0	869.5
Current Liabilities
Long-term Debt Due Within One Year	243.7	236.1
Accrued Interest	13.4	15.9
Noncurrent Liabilities
Long-term Debt	658.9	790.1
Appalachian Power Co [Member]
Current Assets
Cash and Cash Equivalents	2.8	2.9
Restricted Cash	17.7	16.3
Fuel	69.4	89.3
Property, Plant and Equipment
Other Property, Plant and Equipment	450.8	427.9
Accumulated Depreciation and Amortization	4,028.8	3,896.4
Other Noncurrent Assets
Securitized Transition Assets	270.4	282.3
Current Liabilities
Long-term Debt Due Within One Year	530.5	249.2
Accrued Interest	41.1	40.5
Noncurrent Liabilities
Long-term Debt	$ 3,543.2	$ 3,730.9
Equity
Common Stock, Shares Authorized	30,000,000	30,000,000
Common Stock, Shares Outstanding	13,499,500	13,499,500
Indiana Michigan Power Co [Member]
Current Assets
Cash and Cash Equivalents	$ 1.4	$ 1.3
Fuel	33.1	31.4
Property, Plant and Equipment
Other Property, Plant and Equipment	595.8	595.2
Accumulated Depreciation and Amortization	3,057.3	3,024.2
Current Liabilities
Long-term Debt Due Within One Year	657.6	474.7
Accrued Interest	40.0	37.5
Noncurrent Liabilities
Long-term Debt	$ 2,439.2	$ 2,270.4
Equity
Common Stock, No Par Value	$ 0	$ 0
Common Stock, Shares Authorized	2,500,000	2,500,000
Common Stock, Shares Outstanding	1,400,000	1,400,000
Indiana Michigan Power Co [Member] | DCC Fuel [Member]
Current Liabilities
Long-term Debt Due Within One Year	$ 104.2	$ 96.3
Ohio Power Co [Member]
Current Assets
Cash and Cash Equivalents	3.3	3.1
Restricted Cash	26.5	26.6
Property, Plant and Equipment
Other Property, Plant and Equipment	532.6	495.9
Accumulated Depreciation and Amortization	2,218.6	2,184.8
Other Noncurrent Assets
Securitized Transition Assets	25.1	37.7
Current Liabilities
Long-term Debt Due Within One Year	47.5	397.0
Noncurrent Liabilities
Long-term Debt	$ 1,692.5	$ 1,322.3
Equity
Common Stock, No Par Value	$ 0	$ 0
Common Stock, Shares Authorized	40,000,000	40,000,000
Common Stock, Shares Outstanding	27,952,473	27,952,473
Ohio Power Co [Member] | Ohio Phase-In-Recovery Funding [Member]
Current Liabilities
Long-term Debt Due Within One Year	$ 47.5	$ 47.0
Noncurrent Liabilities
Long-term Debt	24.3	47.5
Public Service Co Of Oklahoma [Member]
Current Assets
Cash and Cash Equivalents	1.6	1.6
Fuel	11.8	12.5
Property, Plant and Equipment
Other Property, Plant and Equipment	301.4	287.4
Accumulated Depreciation and Amortization	1,439.3	1,393.6
Current Liabilities
Long-term Debt Due Within One Year	0.5	0.5
Accrued Interest	13.3	14.1
Noncurrent Liabilities
Long-term Debt	$ 1,286.3	$ 1,286.0
Equity
Common Stock, Par Value Per Share	$ 15	$ 15
Common Stock, Shares Authorized	11,000,000	11,000,000
Common Stock, Shares, Issued	10,482,000	10,482,000
Common Stock, Shares Outstanding	9,013,000	9,013,000
Southwestern Electric Power Co [Member]
Current Assets
Cash and Cash Equivalents	$ 2.1	$ 1.6
Fuel	121.2	123.6
Property, Plant and Equipment
Other Property, Plant and Equipment	733.9	684.1
Accumulated Depreciation and Amortization	2,759.3	2,685.8
Current Liabilities
Long-term Debt Due Within One Year	457.2	3.7
Accrued Interest	39.0	38.9
Noncurrent Liabilities
Long-term Debt	$ 2,046.5	$ 2,438.2
Equity
Common Stock, Par Value Per Share	$ 18	$ 18
Common Stock, Shares Authorized	7,600,000	7,600,000
Common Stock, Shares Outstanding	7,536,640	7,536,640
Southwestern Electric Power Co [Member] | Sabine Mining Co [Member]
Current Assets
Fuel	$ 37.8	$ 41.5
Property, Plant and Equipment
Other Property, Plant and Equipment	265.6	266.7
Accumulated Depreciation and Amortization	$ 171.0	$ 165.9