Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Current Assets
Cash and Cash Equivalents	$ 227.7	$ 234.1
Restricted Cash	135.4	210.0
Other Temporary Investments	168.9	159.1
Fuel	360.3	341.5
Property, Plant and Equipment
Other Property, Plant and Equipment	4,202.7	4,265.0
Accumulated Depreciation and Amortization	18,182.6	17,986.1
Assets, Noncurrent [Abstract]
Securitized Assets	853.0	920.6
Current Liabilities
Long-term Debt Due Within One Year	1,528.5	1,698.5
Accrued Interest	306.0	231.7
Noncurrent Liabilities
Long-term Debt	$ 22,898.2	$ 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	513,632,124	513,450,036
Treasury Stock, Shares	20,204,160	20,204,160
AEP Subsidiaries [Member]
Current Assets
Restricted Cash	$ 135.4	$ 210.0
Other Temporary Investments	159.1	152.7
Current Liabilities
Long-term Debt Due Within One Year	375.9	406.5
Noncurrent Liabilities
Long-term Debt	980.0	1,109.2
AEP Texas Inc. [Member]
Current Assets
Cash and Cash Equivalents	0.1	3.1
Restricted Cash	100.6	156.7
Fuel	8.5	8.8
Property, Plant and Equipment
Other Property, Plant and Equipment	734.5	727.9
Accumulated Depreciation and Amortization	1,686.6	1,651.2
Assets, Noncurrent [Abstract]
Securitized Assets	592.9	649.1
Current Liabilities
Long-term Debt Due Within One Year	508.6	501.1
Accrued Interest	50.7	37.3
Noncurrent Liabilities
Long-term Debt	3,269.7	3,380.2
AEP Texas Inc. [Member] | AEP Texas Central Transition Funding Co [Member]
Assets, Noncurrent [Abstract]
Securitized Assets	582.8	636.8
Current Liabilities
Long-term Debt Due Within One Year	258.6	251.1
Accrued Interest	7.4	11.3
Noncurrent Liabilities
Long-term Debt	429.4	540.1
AEP Transmission Co [Member]
Current Assets
Cash and Cash Equivalents	0.0	0.0
Property, Plant and Equipment
Other Property, Plant and Equipment	174.4	174.0
Accumulated Depreciation and Amortization	306.7	271.9
Current Liabilities
Long-term Debt Due Within One Year	85.0	85.0
Accrued Interest	35.1	15.9
Noncurrent Liabilities
Long-term Debt	2,738.4	2,738.0
Appalachian Power Co [Member]
Current Assets
Cash and Cash Equivalents	2.9	4.2
Restricted Cash	18.3	25.6
Fuel	69.9	61.3
Property, Plant and Equipment
Other Property, Plant and Equipment	504.5	485.8
Accumulated Depreciation and Amortization	4,174.9	4,124.4
Assets, Noncurrent [Abstract]
Securitized Assets	252.7	258.7
Current Liabilities
Long-term Debt Due Within One Year	345.0	430.7
Accrued Interest	74.2	41.5
Noncurrent Liabilities
Long-term Debt	$ 4,099.0	$ 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	$ 1.7	$ 2.4
Fuel	32.0	37.3
Property, Plant and Equipment
Other Property, Plant and Equipment	580.1	583.8
Accumulated Depreciation and Amortization	3,208.4	3,151.6
Current Liabilities
Long-term Debt Due Within One Year	140.4	155.4
Accrued Interest	20.9	37.3
Noncurrent Liabilities
Long-term Debt	$ 2,871.0	$ 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	$ 61.8	$ 76.8
Ohio Power Co [Member]
Current Assets
Cash and Cash Equivalents	3.3	4.9
Restricted Cash	16.5	27.6
Property, Plant and Equipment
Other Property, Plant and Equipment	580.0	574.8
Accumulated Depreciation and Amortization	2,224.1	2,218.6
Assets, Noncurrent [Abstract]
Securitized Assets	7.3	12.9
Current Liabilities
Long-term Debt Due Within One Year	24.6	47.9
Noncurrent Liabilities
Long-term Debt	$ 1,669.0	$ 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	$ 24.5	$ 47.8
Public Service Co Of Oklahoma [Member]
Current Assets
Cash and Cash Equivalents	1.5	2.0
Fuel	10.0	12.3
Property, Plant and Equipment
Other Property, Plant and Equipment	306.0	303.5
Accumulated Depreciation and Amortization	1,496.2	1,472.9
Current Liabilities
Long-term Debt Due Within One Year	375.5	375.5
Noncurrent Liabilities
Long-term Debt	$ 1,010.7	$ 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	$ 22.1	$ 24.5
Fuel	135.1	120.5
Property, Plant and Equipment
Other Property, Plant and Equipment	658.9	762.7
Accumulated Depreciation and Amortization	2,760.6	2,808.3
Current Liabilities
Long-term Debt Due Within One Year	6.2	59.7
Accrued Interest	22.0	34.7
Noncurrent Liabilities
Long-term Debt	$ 2,652.9	$ 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	$ 20.2	$ 22.0
Fuel	31.4	35.7
Property, Plant and Equipment
Other Property, Plant and Equipment	210.0	276.9
Accumulated Depreciation and Amortization	$ 99.3	$ 174.6