Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current Assets
Cash and Cash Equivalents	$ 183.4	$ 214.6
Restricted Cash	133.1	198.0
Other Temporary Investments	167.9	161.7
Fuel	359.6	387.7
Property, Plant and Equipment
Other Property, Plant and Equipment	3,812.5	3,706.3
Accumulated Depreciation and Amortization	17,431.2	17,167.0
Assets, Noncurrent [Abstract]
Securitized Assets	1,146.6	1,211.2
Current Liabilities
Long-term Debt Due Within One Year	2,616.1	1,753.7
Accrued Interest	273.1	234.5
Noncurrent Liabilities
Long-term Debt	$ 18,844.9	$ 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	512,716,170	512,210,644
Treasury Stock, Shares	20,204,160	20,205,046
AEP Subsidiaries [Member]
Current Assets
Restricted Cash	$ 133.1	$ 198.0
Other Temporary Investments	155.8	155.4
Current Liabilities
Long-term Debt Due Within One Year	406.5	406.9
Noncurrent Liabilities
Long-term Debt	1,253.0	1,410.5
AEP Texas Inc. [Member]
Current Assets
Cash and Cash Equivalents	0.1	2.0
Restricted Cash	107.1	155.2
Fuel	6.4	3.6
Property, Plant and Equipment
Other Property, Plant and Equipment	475.4	461.0
Accumulated Depreciation and Amortization	1,617.4	1,594.5
Assets, Noncurrent [Abstract]
Securitized Assets	838.9	891.2
Current Liabilities
Long-term Debt Due Within One Year	273.1	266.1
Accrued Interest	48.0	42.2
Noncurrent Liabilities
Long-term Debt	3,280.2	3,383.2
AEP Texas Inc. [Member] | AEP Texas Central Transition Funding Co [Member]
Assets, Noncurrent [Abstract]
Securitized Assets	819.2	869.5
Current Liabilities
Long-term Debt Due Within One Year	243.1	236.1
Accrued Interest	10.2	15.9
Noncurrent Liabilities
Long-term Debt	686.8	790.1
AEP Transmission Co [Member]
Current Assets
Cash and Cash Equivalents	0.0	0.0
Property, Plant and Equipment
Other Property, Plant and Equipment	137.1	131.4
Accumulated Depreciation and Amortization	192.7	170.4
Current Liabilities
Long-term Debt Due Within One Year	50.0	50.0
Accrued Interest	38.3	15.0
Noncurrent Liabilities
Long-term Debt	2,500.7	2,500.4
Appalachian Power Co [Member]
Current Assets
Cash and Cash Equivalents	1.2	2.9
Restricted Cash	10.1	16.3
Fuel	72.1	89.3
Property, Plant and Equipment
Other Property, Plant and Equipment	440.2	427.9
Accumulated Depreciation and Amortization	3,956.8	3,896.4
Assets, Noncurrent [Abstract]
Securitized Assets	276.4	282.3
Current Liabilities
Long-term Debt Due Within One Year	249.5	249.2
Accrued Interest	62.9	40.5
Noncurrent Liabilities
Long-term Debt	$ 3,719.8	$ 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	$ 0.6	$ 1.3
Fuel	35.2	31.4
Property, Plant and Equipment
Other Property, Plant and Equipment	610.9	595.2
Accumulated Depreciation and Amortization	3,073.1	3,024.2
Current Liabilities
Long-term Debt Due Within One Year	941.5	474.7
Accrued Interest	14.8	37.5
Noncurrent Liabilities
Long-term Debt	$ 1,775.7	$ 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	$ 88.1	$ 96.3
Ohio Power Co [Member]
Current Assets
Cash and Cash Equivalents	1.4	3.1
Restricted Cash	15.9	26.6
Property, Plant and Equipment
Other Property, Plant and Equipment	518.9	495.9
Accumulated Depreciation and Amortization	2,205.7	2,184.8
Assets, Noncurrent [Abstract]
Securitized Assets	31.4	37.7
Current Liabilities
Long-term Debt Due Within One Year	397.5	397.0
Accrued Interest	38.7	31.0
Noncurrent Liabilities
Long-term Debt	$ 1,692.2	$ 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	0.6	1.6
Fuel	13.0	12.5
Property, Plant and Equipment
Other Property, Plant and Equipment	297.0	287.4
Accumulated Depreciation and Amortization	1,415.5	1,393.6
Current Liabilities
Long-term Debt Due Within One Year	0.5	0.5
Accrued Interest	19.3	14.1
Noncurrent Liabilities
Long-term Debt	$ 1,286.2	$ 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	$ 0.7	$ 1.6
Fuel	120.5	123.6
Property, Plant and Equipment
Other Property, Plant and Equipment	704.4	684.1
Accumulated Depreciation and Amortization	2,724.7	2,685.8
Current Liabilities
Long-term Debt Due Within One Year	457.2	3.7
Accrued Interest	25.9	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	$ 37.7	$ 41.5
Property, Plant and Equipment
Other Property, Plant and Equipment	264.9	266.7
Accumulated Depreciation and Amortization	$ 167.4	$ 165.9