Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and Cash Equivalents	$ 788.3	$ 214.6
Restricted Cash	149.2	198.0
Other Temporary Investments	164.1	161.7
Fuel	282.3	387.7
Property, Plant and Equipment
Other Property, Plant and Equipment	3,996.9	3,706.3
Accumulated Depreciation and Amortization	17,841.6	17,167.0
Other Noncurrent Assets
Securitized Transition Assets	1,001.4	1,211.2
Current Liabilities
Long-term Debt Due Within One Year	1,904.2	1,753.7
Accrued Interest	299.8	234.5
Noncurrent Liabilities
Long-term Debt	$ 20,869.8	$ 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	513,301,636	512,210,644
Treasury Stock, Shares	20,204,160	20,205,046
AEP Subsidiaries [Member]
Current Assets
Restricted Cash	$ 149.2	$ 198.0
Other Temporary Investments	157.0	155.4
Current Liabilities
Long-term Debt Due Within One Year	420.7	406.9
Noncurrent Liabilities
Long-term Debt	1,110.0	1,410.5
AEP Texas Inc. [Member]
Current Assets
Cash and Cash Equivalents	0.1	2.0
Restricted Cash	124.2	155.2
Fuel	6.9	3.6
Property, Plant and Equipment
Other Property, Plant and Equipment	554.0	461.0
Accumulated Depreciation and Amortization	1,643.9	1,594.5
Other Noncurrent Assets
Securitized Transition Assets	717.9	891.2
Current Liabilities
Long-term Debt Due Within One Year	500.5	266.1
Accrued Interest	54.3	42.2
Noncurrent Liabilities
Long-term Debt	3,413.9	3,383.2
AEP Texas Inc. [Member] | AEP Texas Central Transition Funding Co [Member]
Other Noncurrent Assets
Securitized Transition Assets	702.9	869.5
Current Liabilities
Long-term Debt Due Within One Year	250.5	236.1
Accrued Interest	9.0	15.9
Noncurrent Liabilities
Long-term Debt	574.7	790.1
Appalachian Power Co [Member]
Current Assets
Cash and Cash Equivalents	2.2	2.9
Restricted Cash	9.9	16.3
Fuel	37.7	89.3
Property, Plant and Equipment
Other Property, Plant and Equipment	461.4	427.9
Accumulated Depreciation and Amortization	4,086.2	3,896.4
Other Noncurrent Assets
Securitized Transition Assets	264.5	282.3
Current Liabilities
Long-term Debt Due Within One Year	430.7	249.2
Accrued Interest	72.6	40.5
Noncurrent Liabilities
Long-term Debt	$ 3,631.0	$ 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	$ 1.6	$ 1.3
Fuel	28.7	31.4
Property, Plant and Equipment
Other Property, Plant and Equipment	584.7	595.2
Accumulated Depreciation and Amortization	3,113.9	3,024.2
Current Liabilities
Long-term Debt Due Within One Year	172.7	474.7
Accrued Interest	22.2	37.5
Noncurrent Liabilities
Long-term Debt	$ 2,889.7	$ 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	$ 94.2	$ 96.3
Ohio Power Co [Member]
Current Assets
Cash and Cash Equivalents	3.5	3.1
Restricted Cash	15.2	26.6
Property, Plant and Equipment
Other Property, Plant and Equipment	547.5	495.9
Accumulated Depreciation and Amortization	2,230.6	2,184.8
Other Noncurrent Assets
Securitized Transition Assets	19.0	37.7
Current Liabilities
Long-term Debt Due Within One Year	47.8	397.0
Noncurrent Liabilities
Long-term Debt	$ 1,668.5	$ 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	$ 47.7	$ 47.0
Noncurrent Liabilities
Long-term Debt	0.0	47.5
Public Service Co Of Oklahoma [Member]
Current Assets
Cash and Cash Equivalents	1.9	1.6
Fuel	12.6	12.5
Property, Plant and Equipment
Other Property, Plant and Equipment	308.3	287.4
Accumulated Depreciation and Amortization	1,461.2	1,393.6
Current Liabilities
Long-term Debt Due Within One Year	0.5	0.5
Accrued Interest	18.9	14.1
Noncurrent Liabilities
Long-term Debt	$ 1,286.4	$ 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	$ 2.5	$ 1.6
Fuel	117.5	123.6
Property, Plant and Equipment
Other Property, Plant and Equipment	744.4	684.1
Accumulated Depreciation and Amortization	2,798.9	2,685.8
Current Liabilities
Long-term Debt Due Within One Year	457.2	3.7
Accrued Interest	27.5	38.9
Noncurrent Liabilities
Long-term Debt	$ 2,615.5	$ 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	$ 33.4	$ 41.5
Property, Plant and Equipment
Other Property, Plant and Equipment	269.6	266.7
Accumulated Depreciation and Amortization	$ 174.7	$ 165.9