Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current Assets
Cash and Cash Equivalents	$ 343.9	$ 210.5
Other Temporary Investments	310.7	331.7
Fuel	354.2	423.8
Property, Plant and Equipment
Other Property, Plant and Equipment	3,614.1	3,444.3
Accumulated Depreciation and Amortization	17,121.7	16,397.3
Current Liabilities
Long-term Debt Due Within One Year	2,359.3	2,878.0
Noncurrent Liabilities
Long-term Debt	$ 18,362.4	$ 17,378.4
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	512,048,663	512,048,520
Treasury Stock, Shares	20,206,368	20,336,592
AEP Subsidiaries [Member]
Current Assets
Other Temporary Investments	$ 300.5	$ 322.5
Current Liabilities
Long-term Debt Due Within One Year	393.7	427.5
Noncurrent Liabilities
Long-term Debt	1,421.5	1,737.5
Appalachian Power Co [Member]
Current Assets
Cash and Cash Equivalents	2.9	2.7
Fuel	96.3	112.0
Property, Plant and Equipment
Other Property, Plant and Equipment	409.8	373.5
Accumulated Depreciation and Amortization	3,836.7	3,636.8
Current Liabilities
Long-term Debt Due Within One Year	149.2	503.1
Noncurrent Liabilities
Long-term Debt	$ 3,830.1	$ 3,530.8
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	$ 1.3	$ 1.2
Fuel	32.3	32.3
Property, Plant and Equipment
Other Property, Plant and Equipment	555.9	550.2
Accumulated Depreciation and Amortization	3,022.5	3,005.1
Current Liabilities
Long-term Debt Due Within One Year	462.1	209.3
Noncurrent Liabilities
Long-term Debt	$ 2,196.4	$ 2,262.1
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	$ 83.7	$ 130.9
Ohio Power Co [Member]
Current Assets
Cash and Cash Equivalents	3.1	3.1
Property, Plant and Equipment
Other Property, Plant and Equipment	487.9	443.7
Accumulated Depreciation and Amortization	2,182.8	2,116.0
Current Liabilities
Long-term Debt Due Within One Year	397.0	46.4
Noncurrent Liabilities
Long-term Debt	$ 1,321.9	$ 1,717.5
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	$ 47.0	$ 46.3
Noncurrent Liabilities
Long-term Debt	47.5	93.9
Public Service Co Of Oklahoma [Member]
Current Assets
Cash and Cash Equivalents	2.1	1.5
Fuel	11.9	22.9
Property, Plant and Equipment
Other Property, Plant and Equipment	286.3	233.2
Accumulated Depreciation and Amortization	1,382.8	1,272.7
Current Liabilities
Long-term Debt Due Within One Year	0.5	0.5
Noncurrent Liabilities
Long-term Debt	$ 1,285.9	$ 1,285.5
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	$ 2.2	$ 10.3
Fuel	93.1	107.1
Property, Plant and Equipment
Other Property, Plant and Equipment	701.6	670.4
Accumulated Depreciation and Amortization	2,670.5	2,567.1
Current Liabilities
Long-term Debt Due Within One Year	385.4	353.7
Noncurrent Liabilities
Long-term Debt	$ 2,056.1	$ 2,325.4
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	$ 0.0	$ 8.7
Fuel	43.2	34.3
Property, Plant and Equipment
Other Property, Plant and Equipment	266.6	267.5
Accumulated Depreciation and Amortization	$ 162.8	$ 155.6