Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Current Assets
Cash and Cash Equivalents	$ 348.8	$ 234.1
Restricted Cash	141.0	210.0
Other Temporary Investments	198.4	159.1
Fuel	437.8	341.5
Property, Plant and Equipment
Other Property, Plant and Equipment	4,510.2	4,265.0
Accumulated Depreciation and Amortization	18,760.2	17,986.1
Other Noncurrent Assets
Securitized Transition Assets	938.7	920.6
Current Liabilities
Long-term Debt Due Within One Year	1,327.7	1,698.5
Accrued Interest	304.8	231.7
Noncurrent Liabilities
Long-term Debt	$ 24,553.5	$ 21,648.2
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	514,140,235	513,450,036
Treasury Stock, Shares	20,204,160	20,204,160
AEP Subsidiaries [Member]
Current Assets
Restricted Cash	$ 141.0	$ 210.0
Other Temporary Investments	193.4	152.7
Current Liabilities
Long-term Debt Due Within One Year	544.7	406.5
Noncurrent Liabilities
Long-term Debt	918.4	1,109.2
AEP Texas Inc. [Member]
Current Assets
Cash and Cash Equivalents	0.1	3.1
Restricted Cash	114.3	156.7
Fuel	7.1	8.8
Property, Plant and Equipment
Other Property, Plant and Equipment	775.3	727.9
Accumulated Depreciation and Amortization	1,742.7	1,651.2
Other Noncurrent Assets
Securitized Transition Assets	698.1	649.1
Current Liabilities
Long-term Debt Due Within One Year	391.4	501.1
Accrued Interest	50.6	37.3
Noncurrent Liabilities
Long-term Debt	3,755.1	3,380.2
AEP Texas Inc. [Member] | AEP Texas Transition Funding and Restoration Funding [Member]
Other Noncurrent Assets
Securitized Transition Assets	693.0	636.8
Current Liabilities
Long-term Debt Due Within One Year	280.8	251.1
Accrued Interest	6.1	11.3
Noncurrent Liabilities
Long-term Debt	530.5	540.1
Appalachian Power Co [Member]
Current Assets
Cash and Cash Equivalents	3.5	4.2
Restricted Cash	17.1	25.6
Fuel	108.8	61.3
Property, Plant and Equipment
Other Property, Plant and Equipment	525.3	485.8
Accumulated Depreciation and Amortization	4,300.2	4,124.4
Other Noncurrent Assets
Securitized Transition Assets	240.6	258.7
Current Liabilities
Long-term Debt Due Within One Year	215.6	430.7
Accrued Interest	67.5	41.5
Noncurrent Liabilities
Long-term Debt	$ 4,147.3	$ 3,631.9
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	$ 2.5	$ 2.4
Fuel	39.8	37.3
Property, Plant and Equipment
Other Property, Plant and Equipment	607.2	583.8
Accumulated Depreciation and Amortization	3,280.5	3,151.6
Current Liabilities
Long-term Debt Due Within One Year	147.4	155.4
Accrued Interest	20.5	37.3
Noncurrent Liabilities
Long-term Debt	$ 2,884.1	$ 2,880.0
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	$ 68.8	$ 76.8
Ohio Power Co [Member]
Current Assets
Cash and Cash Equivalents	4.7	4.9
Restricted Cash	0.0	27.6
Property, Plant and Equipment
Other Property, Plant and Equipment	662.3	574.8
Accumulated Depreciation and Amortization	2,256.1	2,218.6
Other Noncurrent Assets
Securitized Transition Assets	0.0	12.9
Current Liabilities
Long-term Debt Due Within One Year	0.1	47.9
Accrued Interest	44.7	31.4
Noncurrent Liabilities
Long-term Debt	$ 2,113.8	$ 1,668.7
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	$ 0.0	$ 47.8
Public Service Co Of Oklahoma [Member]
Current Assets
Cash and Cash Equivalents	2.9	2.0
Fuel	12.8	12.3
Property, Plant and Equipment
Other Property, Plant and Equipment	319.6	303.5
Accumulated Depreciation and Amortization	1,558.5	1,472.9
Current Liabilities
Long-term Debt Due Within One Year	138.2	375.5
Noncurrent Liabilities
Long-term Debt	$ 1,248.2	$ 911.5
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	$ 21.4	$ 24.5
Fuel	135.9	120.5
Property, Plant and Equipment
Other Property, Plant and Equipment	703.2	762.7
Accumulated Depreciation and Amortization	2,848.2	2,808.3
Current Liabilities
Long-term Debt Due Within One Year	121.2	59.7
Accrued Interest	22.9	34.7
Noncurrent Liabilities
Long-term Debt	$ 2,535.7	$ 2,653.7
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
Cash and Cash Equivalents	$ 18.2	$ 22.0
Fuel	51.6	35.7
Property, Plant and Equipment
Other Property, Plant and Equipment	210.3	276.9
Accumulated Depreciation and Amortization	$ 105.7	$ 174.6