Significant Accounting Matters (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended				9 Months Ended				63 Months Ended	81 Months Ended	90 Months Ended
		Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017		Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Amounts Attributable to AEP Common Shareholders
Net Income Attributable to Noncontrolling Interests		$ 2.1		$ 12.0		$ 6.1		$ 15.2
Net Income (Loss) Available to Common Stockholders, Basic		$ 577.6		$ 544.7		$ 1,560.4		$ 1,511.9
Weighted Average Number of Basic AEP Common Shares Outstanding		492,984,741		491,840,722		492,649,456		491,781,643
Basic Earnings Per Share Attributable to AEP Common Shareholders from Continuing Operations		$ 1.17		$ 1.11		$ 3.17		$ 3.07
Weighted Average Dilutive Effect of:
Weighted Average Number of Diluted AEP Common Shares Outstanding		493,940,543		492,986,307		493,526,937		492,428,586
Diluted Earnings Per Share Attributable to AEP Common Shareholders from Continuing Operations		$ 1.17		$ 1.10		$ 3.16		$ 3.07
Antidilutive Shares Outstanding						0		0
Income (Loss) from Equity Method Investments Adjustment						$ 6.0
Net Income (Loss)		$ 579.7		$ 556.7		1,566.5		$ 1,527.1
Retained Earnings (Accumulated Deficit)													$ 9,293.7	$ 8,626.7
Revenues
TOTAL REVENUES		4,333.1		4,104.7		12,394.6		11,614.5
Expenses
Depreciation and Amortization		602.6		518.5		1,695.5		1,485.9
TOTAL EXPENSES		3,664.5		3,129.6		10,263.0		8,820.4
OPERATING INCOME (LOSS)		668.6		975.1		2,131.6		2,794.1
Other Income (Expense):
Allowance for Equity Funds Used During Construction		30.9		20.0		92.4		62.2
Interest Expense		(256.8)		(223.3)		(733.1)		(668.0)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		480.9		800.6		1,604.7		2,261.8
Income Tax Expense (Credit)		(80.7)		264.0		93.5		797.8
Net Income (Loss)		579.7		556.7		1,566.5		1,527.1
Accounts Receivable:
Customers													757.9	643.9
Total Accounts Receivable													2,118.1	1,891.0
TOTAL CURRENT ASSETS													4,692.4	4,253.1
Property, Plant and Equipment
Transmission													20,113.7	18,972.5
Other Property, Plant and Equipment													3,996.9	3,706.3
Construction Work in Progress													4,995.5	4,120.7
Total Property, Plant and Equipment													71,197.3	67,428.5
Accumulated Depreciation and Amortization													17,841.6	17,167.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													53,355.7	50,261.5
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													9,569.3	10,214.5
TOTAL ASSETS													67,617.4	64,729.1
Liabilities, Current [Abstract]
Accounts Payable													1,579.9	2,065.3
Accrued Taxes													774.1	1,115.5
TOTAL CURRENT LIABILITIES													8,426.2	8,271.3
Noncurrent Liabilities
Deferred Income Taxes													7,110.4	6,813.9
Regulatory Liabilities and Deferred Investment Tax Credits													8,643.5	8,422.3
TOTAL NONCURRENT LIABILITIES													40,043.9	38,132.3
TOTAL LIABILITIES													48,470.1	46,403.6
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													67,617.4	64,729.1
Operating Activities
Net Income (Loss)		579.7		556.7		1,566.5		1,527.1
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		602.6		518.5		1,695.5		1,485.9
Deferred Income Taxes						43.0		740.9
Allowance for Equity Funds Used During Construction		(30.9)		(20.0)		(92.4)		(62.2)
Property Taxes						304.8		291.4
Change in Other Noncurrent Assets						161.6		(334.6)
Change in Other Noncurrent Liabilities						141.9		205.7
Accounts Receivable, Net						(52.3)		201.3
Fuel, Materials and Supplies						98.7		58.5
Accounts Payable						(45.0)		(91.0)
Accrued Taxes, Net						(247.5)		(310.1)
Other Current Assets						11.7		(98.2)
Other Current Liabilities						101.1		(260.3)
Net Cash Flows from (Used for) Operating Activities						3,932.6		3,124.2
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(4,688.7)		(1,722.7)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						1,281.0		(1,314.2)
Cash and Cash Equivalents at Beginning of Period						214.6
Cash and Cash Equivalents at End of Period		788.3				788.3
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						631.3		613.8
Net Cash Paid (Received) for Income Taxes						(27.9)		(6.8)
Construction Expenditures Included in Current Liabilities as of September 30,						882.3		791.6
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		788.3				214.6							788.3	214.6
Restricted Cash													149.2	198.0
Total Cash, Cash Equivalents and Restricted Cash													937.5	412.6
Total Cash, Cash Equivalents and Restricted Cash													937.5	412.6	$ 490.8	$ 403.5
AEP Texas Inc. [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)		57.8		64.3		151.1		146.6
Retained Earnings (Accumulated Deficit)													1,277.5	1,124.6
Revenues
TOTAL REVENUES		433.4		431.2		1,193.3		1,164.3
Expenses
Depreciation and Amortization		133.3		124.0		364.9		343.0
TOTAL EXPENSES		339.4		302.4		931.3		844.4
OPERATING INCOME (LOSS)		94.0		128.8		262.0		319.9
Other Income (Expense):
Allowance for Equity Funds Used During Construction		5.8		0.0		15.2		2.2
Interest Expense		(37.3)		(35.3)		(108.9)		(105.6)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		66.1		94.9		177.5		220.8
Income Tax Expense (Credit)		8.3		30.6		26.4		74.2
Net Income (Loss)		57.8		64.3		151.1		146.6
Accounts Receivable:
Customers													132.9	105.3
Total Accounts Receivable													220.5	194.0
Accrued Tax Benefits													14.6	41.0
TOTAL CURRENT ASSETS													437.9	563.8
Property, Plant and Equipment
Transmission													3,302.3	3,053.6
Other Property, Plant and Equipment													554.0	461.0
Construction Work in Progress													1,108.8	835.7
Total Property, Plant and Equipment													9,285.6	8,419.6
Accumulated Depreciation and Amortization													1,643.9	1,594.5
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													7,641.7	6,825.1
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													1,212.1	1,384.7
TOTAL ASSETS													9,291.7	8,773.6
Liabilities, Current [Abstract]
Accounts Payable													208.8	379.4
Affiliated Companies													31.7	30.2
Accrued Taxes													90.8	77.2
TOTAL CURRENT LIABILITIES													1,086.2	871.5
Noncurrent Liabilities
Deferred Income Taxes													902.3	913.1
Regulatory Liabilities and Deferred Investment Tax Credits													1,346.4	1,320.5
TOTAL NONCURRENT LIABILITIES													5,784.5	5,732.2
TOTAL LIABILITIES													6,870.7	6,603.7
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													9,291.7	8,773.6
Operating Activities
Net Income (Loss)		57.8		64.3		151.1		146.6
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		133.3		124.0		364.9		343.0
Deferred Income Taxes						(21.2)		124.1
Allowance for Equity Funds Used During Construction		(5.8)		0.0		(15.2)		(2.2)
Property Taxes						(19.2)		(15.9)
Change in Other Noncurrent Assets						(14.2)		(29.1)
Change in Other Noncurrent Liabilities						67.1		7.4
Accounts Receivable, Net						(26.5)		(47.6)
Fuel, Materials and Supplies						(2.4)		(0.1)
Accounts Payable						(19.1)		77.3
Accrued Taxes, Net						40.0		1.7
Other Current Assets						(6.3)		(2.5)
Other Current Liabilities						14.1		(31.2)
Net Cash Flows from (Used for) Operating Activities						490.8		490.5
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(961.1)		(1,043.0)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						437.4		528.7
Cash and Cash Equivalents at Beginning of Period						2.0
Cash and Cash Equivalents at End of Period		0.1				0.1
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						92.2		101.1
Net Cash Paid (Received) for Income Taxes						(14.2)		(23.3)
Construction Expenditures Included in Current Liabilities as of September 30,						176.4		166.1
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		0.1				2.0							0.1	2.0
Restricted Cash													124.2	155.2
Total Cash, Cash Equivalents and Restricted Cash													124.3	157.2
Total Cash, Cash Equivalents and Restricted Cash													124.3	157.2	123.1	146.9
AEP Transmission Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)		78.1		58.6	[1]	244.2	[1]	212.4	[1]
Retained Earnings (Accumulated Deficit)													1,017.5	773.3
Revenues
TOTAL REVENUES		194.4	[2]	165.6	[1]	586.2	[1],[2]	534.8	[1]
Expenses
Depreciation and Amortization		34.9		24.6		97.5		69.7
TOTAL EXPENSES		97.4		72.0		267.6		197.3
OPERATING INCOME (LOSS)		97.0		93.6		318.6		337.5
Other Income (Expense):
Allowance for Equity Funds Used During Construction		18.0		11.4		48.7		33.0
Interest Expense		(19.8)		(17.1)	[1]	(60.7)	[1]	(50.4)	[1]
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		95.7		88.1		307.9		320.6
Income Tax Expense (Credit)		17.6		29.5	[1]	63.7	[1]	108.2	[1]
Net Income (Loss)		78.1		58.6	[1]	244.2	[1]	212.4	[1]
Accounts Receivable:
Customers													11.9	15.0
Total Accounts Receivable													86.0	109.5
Accrued Tax Benefits													29.8	49.4
TOTAL CURRENT ASSETS													413.7	326.4
Property, Plant and Equipment
Transmission													5,833.5	5,319.7
Other Property, Plant and Equipment													155.2	126.8
Construction Work in Progress													1,772.9	1,324.0
Total Property, Plant and Equipment	[1]												7,761.6	6,770.5
Accumulated Depreciation and Amortization	[1]												234.6	152.6
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET	[1]												7,527.0	6,617.9
Other Noncurrent Assets
Deferred Property Taxes													38.1	125.0
TOTAL OTHER NONCURRENT ASSETS													57.7	137.8
TOTAL ASSETS	[1]												7,998.4	7,082.1
Liabilities, Current [Abstract]
Accounts Payable													237.4	484.5
Affiliated Companies													79.0	66.1
Accrued Taxes													138.7	231.5
TOTAL CURRENT LIABILITIES													546.4	866.9
Noncurrent Liabilities
Deferred Income Taxes													684.4	600.4
Regulatory Liabilities and Deferred Investment Tax Credits													509.6	493.8
TOTAL NONCURRENT LIABILITIES													4,035.9	3,625.3
TOTAL LIABILITIES													4,582.3	4,492.2
Equity [Abstract]
TOTAL MEMBER'S EQUITY													3,416.1	2,589.9	2,355.5	1,957.6
TOTAL LIABILITIES AND EQUITY													7,998.4	7,082.1
Operating Activities
Net Income (Loss)		78.1		58.6	[1]	244.2	[1]	212.4	[1]
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		34.9		24.6		97.5		69.7
Deferred Income Taxes						76.3		191.9
Allowance for Equity Funds Used During Construction		(18.0)		(11.4)		(48.7)		(33.0)
Property Taxes						86.9		72.4
Long-term Accounts Receivable - Affiliated						(3.1)		(13.8)
Change in Other Noncurrent Assets						12.7		8.6
Change in Other Noncurrent Liabilities						18.0		25.7
Accounts Receivable, Net						23.5		(40.8)
Fuel, Materials and Supplies						(2.8)		(11.0)
Accounts Payable						3.3		20.4
Accrued Taxes, Net						(73.2)		(71.2)
Accrued Interest						20.9		18.4
Other Current Assets						(0.5)		(5.3)
Other Current Liabilities						(28.0)		0.5
Net Cash Flows from (Used for) Operating Activities						427.0		444.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(1,315.5)		(1,277.4)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						888.5		832.5
Net Increase (Decrease) in Cash and Cash Equivalents						0.0		0.0
Cash and Cash Equivalents at Beginning of Period						0.0		0.0
Cash and Cash Equivalents at End of Period		0.0		0.0		0.0		0.0			$ 0.0
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						38.4		30.4
Net Cash Paid (Received) for Income Taxes						(32.1)		(93.4)
Construction Expenditures Included in Current Liabilities as of September 30,						237.0		248.9
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		0.0		0.0		0.0		0.0			0.0		0.0	0.0	0.0	0.0
Appalachian Power Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)		87.1		86.0		290.0		248.7
Retained Earnings (Accumulated Deficit)													1,884.2	1,714.1
Revenues
TOTAL REVENUES		762.0		719.3		2,249.4		2,187.4
Expenses
Depreciation and Amortization		105.7		102.8		319.5		304.1
TOTAL EXPENSES		712.2		547.6		1,874.0		1,670.7
OPERATING INCOME (LOSS)		49.8		171.7		375.4		516.7
Other Income (Expense):
Allowance for Equity Funds Used During Construction		4.1		2.7		9.6		6.2
Interest Expense		(50.8)		(47.2)		(146.0)		(143.5)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		8.2		129.2		254.9		385.4
Income Tax Expense (Credit)		(78.9)		43.2		(35.1)		136.7
Net Income (Loss)		87.1		86.0		290.0		248.7
Accounts Receivable:
Customers													155.7	123.1
Total Accounts Receivable													275.8	263.9
TOTAL CURRENT ASSETS													630.9	636.2
Property, Plant and Equipment
Transmission													3,141.2	3,019.9
Other Property, Plant and Equipment													461.4	427.9
Construction Work in Progress													602.1	483.0
Total Property, Plant and Equipment													14,591.9	14,141.5
Accumulated Depreciation and Amortization													4,086.2	3,896.4
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													10,505.7	10,245.1
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													921.3	1,047.3
TOTAL ASSETS													12,057.9	11,928.6
Liabilities, Current [Abstract]
Accounts Payable													219.1	264.9
Affiliated Companies													73.6	92.7
Accrued Taxes													81.5	94.5
TOTAL CURRENT LIABILITIES													1,216.5	1,124.2
Noncurrent Liabilities
Deferred Income Taxes													1,581.5	1,565.7
Regulatory Liabilities and Deferred Investment Tax Credits													1,423.8	1,454.9
TOTAL NONCURRENT LIABILITIES													6,869.5	6,999.9
TOTAL LIABILITIES													8,086.0	8,124.1
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													12,057.9	11,928.6
Operating Activities
Net Income (Loss)		87.1		86.0		290.0		248.7
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		105.7		102.8		319.5		304.1
Deferred Income Taxes						(83.8)		121.7
Allowance for Equity Funds Used During Construction		(4.1)		(2.7)		(9.6)		(6.2)
Change in Other Noncurrent Assets						94.8		37.1
Change in Other Noncurrent Liabilities						3.8		7.9
Accounts Receivable, Net						39.4		39.9
Fuel, Materials and Supplies						53.0		14.0
Accounts Payable						(21.5)		6.2
Accrued Taxes, Net						(20.2)		(44.2)
Other Current Assets						(7.9)		(2.5)
Other Current Liabilities						64.1		9.1
Net Cash Flows from (Used for) Operating Activities						690.7		702.2
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(565.4)		(547.7)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						(132.4)		(161.8)
Cash and Cash Equivalents at Beginning of Period						2.9
Cash and Cash Equivalents at End of Period		2.2				2.2
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						104.5		107.1
Net Cash Paid (Received) for Income Taxes						26.7		24.4
Construction Expenditures Included in Current Liabilities as of September 30,						87.6		107.2
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		2.2				2.9							2.2	2.9
Restricted Cash													9.9	16.3
Total Cash, Cash Equivalents and Restricted Cash													12.1	19.2	11.2	18.5
Indiana Michigan Power Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)		72.7		64.9		231.6		143.8
Retained Earnings (Accumulated Deficit)													1,318.6	1,192.2
Revenues
TOTAL REVENUES		629.7		557.7		1,796.2		1,585.5
Expenses
Depreciation and Amortization		85.2		55.0		207.1		154.8
TOTAL EXPENSES		519.5		444.1		1,471.2		1,321.1
OPERATING INCOME (LOSS)		110.2		113.6		325.0		264.4
Other Income (Expense):
Allowance for Equity Funds Used During Construction		3.9		3.5		8.0		8.1
Interest Expense		(34.5)		(27.5)		(95.6)		(83.0)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		86.4		93.5		258.4		205.6
Income Tax Expense (Credit)		13.7		28.6		26.8		61.8
Net Income (Loss)		72.7		64.9		231.6		143.8
Accounts Receivable:
Customers													70.5	56.4
Total Accounts Receivable													140.0	115.6
Accrued Tax Benefits													35.4	58.4
TOTAL CURRENT ASSETS													483.7	434.0
Property, Plant and Equipment
Transmission													1,543.3	1,504.0
Other Property, Plant and Equipment													584.7	595.2
Construction Work in Progress													458.6	460.2
Total Property, Plant and Equipment													9,350.4	9,074.6
Accumulated Depreciation and Amortization													3,113.9	3,024.2
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													6,236.5	6,050.4
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													3,387.9	3,287.6
TOTAL ASSETS													10,108.1	9,772.0
Liabilities, Current [Abstract]
Accounts Payable													142.6	154.5
Affiliated Companies													65.6	98.3
Accrued Taxes													44.7	81.3
TOTAL CURRENT LIABILITIES													621.0	1,211.3
Noncurrent Liabilities
Deferred Income Taxes													1,010.0	953.8
Regulatory Liabilities and Deferred Investment Tax Credits													1,791.9	1,708.7
TOTAL NONCURRENT LIABILITIES													7,144.6	6,343.1
TOTAL LIABILITIES													7,765.6	7,554.4
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													10,108.1	9,772.0
Operating Activities
Net Income (Loss)		72.7		64.9		231.6		143.8
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		85.2		55.0		207.1		154.8
Deferred Income Taxes						28.1		132.2
Allowance for Equity Funds Used During Construction		(3.9)		(3.5)		(8.0)		(8.1)
Change in Other Noncurrent Assets						(7.4)		(32.2)
Change in Other Noncurrent Liabilities						46.3		40.9
Accounts Receivable, Net						6.5		19.3
Fuel, Materials and Supplies						(1.1)		(4.1)
Accounts Payable						(34.7)		16.6
Accrued Taxes, Net						(7.1)		(30.2)
Accrued Interest						(15.3)		(17.4)
Other Current Assets						4.9		8.0
Other Current Liabilities						0.3		(14.2)
Net Cash Flows from (Used for) Operating Activities						571.3		524.3
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(549.6)		(568.8)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						(21.4)		44.6
Net Increase (Decrease) in Cash and Cash Equivalents						0.3		0.1
Cash and Cash Equivalents at Beginning of Period						1.3		1.2
Cash and Cash Equivalents at End of Period		1.6		1.3		1.6		1.3			1.3
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						104.4		92.0
Net Cash Paid (Received) for Income Taxes						(26.5)		(69.6)
Construction Expenditures Included in Current Liabilities as of September 30,						66.4		74.5
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		1.6		1.3		1.3		1.2			1.3		1.6	1.3	1.3	1.2
Ohio Power Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)		88.7		82.6		237.1		231.1
Retained Earnings (Accumulated Deficit)													1,048.0	1,148.4
Revenues
TOTAL REVENUES		778.3		742.0		2,318.0		2,152.0
Expenses
Depreciation and Amortization		70.4		57.3		200.3		165.7
TOTAL EXPENSES		698.4		588.6		2,016.4		1,730.5
OPERATING INCOME (LOSS)		79.9		153.4		301.6		421.5
Other Income (Expense):
Allowance for Equity Funds Used During Construction		2.0		0.9		7.8		4.1
Interest Expense		(26.1)		(25.7)		(76.6)		(76.8)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		60.6		130.9		248.5		359.1
Income Tax Expense (Credit)		(28.1)		48.3		11.4		128.0
Net Income (Loss)		88.7		82.6		237.1		231.1
Accounts Receivable:
Customers													116.9	67.8
Total Accounts Receivable													221.5	169.0
TOTAL CURRENT ASSETS													353.1	397.9
Property, Plant and Equipment
Transmission													2,484.5	2,419.2
Other Property, Plant and Equipment													547.5	495.9
Construction Work in Progress													475.7	410.1
Total Property, Plant and Equipment													8,333.3	7,951.6
Accumulated Depreciation and Amortization													2,230.6	2,184.8
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													6,102.7	5,766.8
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													662.8	1,097.0
TOTAL ASSETS													7,118.6	7,261.7
Liabilities, Current [Abstract]
Accounts Payable													169.2	205.8
Affiliated Companies													95.3	118.2
Accrued Taxes													293.8	512.5
TOTAL CURRENT LIABILITIES													1,137.8	1,593.8
Noncurrent Liabilities
Deferred Income Taxes													742.8	762.9
Regulatory Liabilities and Deferred Investment Tax Credits													1,197.7	1,100.2
TOTAL NONCURRENT LIABILITIES													3,771.5	3,357.6
TOTAL LIABILITIES													4,909.3	4,951.4
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													7,118.6	7,261.7
Operating Activities
Net Income (Loss)		88.7		82.6		237.1		231.1
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		70.4		57.3		200.3		165.7
Deferred Income Taxes						(71.9)		117.5
Allowance for Equity Funds Used During Construction		(2.0)		(0.9)		(7.8)		(4.1)
Property Taxes						191.1		175.9
Change in Other Noncurrent Assets						0.8		(44.5)
Change in Other Noncurrent Liabilities						62.5		43.4
Accounts Receivable, Net						21.3		14.9
Fuel, Materials and Supplies						(3.7)		(7.1)
Accounts Payable						(31.8)		(31.2)
Accrued Taxes, Net						(210.6)		(284.3)
Other Current Assets						9.1		(17.3)
Other Current Liabilities						(4.3)		(34.8)
Net Cash Flows from (Used for) Operating Activities						700.8		330.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(523.0)		(331.4)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						(188.8)		(11.1)
Cash and Cash Equivalents at Beginning of Period						3.1
Cash and Cash Equivalents at End of Period		3.5				3.5
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						67.3		68.1
Net Cash Paid (Received) for Income Taxes						54.1		69.6
Construction Expenditures Included in Current Liabilities as of September 30,						66.0		56.8
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		3.5				3.1							3.5	3.1
Restricted Cash													15.2	26.6
Total Cash, Cash Equivalents and Restricted Cash													18.7	29.7	18.7	30.3
Public Service Co Of Oklahoma [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)		60.4		46.2		89.8		71.4
Retained Earnings (Accumulated Deficit)													743.8	691.5
Revenues
TOTAL REVENUES		481.4		442.8		1,216.5		1,091.6
Expenses
Depreciation and Amortization		42.3		31.7		120.5		97.8
TOTAL EXPENSES		402.9		356.9		1,076.9		940.5
OPERATING INCOME (LOSS)		78.5		85.9		139.6		151.1
Other Income (Expense):
Allowance for Equity Funds Used During Construction						(0.3)		0.4
Interest Expense		(16.4)		(13.2)		(47.4)		(40.2)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		64.0		73.6		98.4		114.0
Income Tax Expense (Credit)		3.6		27.4		8.6		42.6
Net Income (Loss)		60.4		46.2		89.8		71.4
Accounts Receivable:
Customers													28.8	32.5
Total Accounts Receivable													72.8	69.4
Accrued Tax Benefits													12.5	28.1
TOTAL CURRENT ASSETS													169.8	205.3
Property, Plant and Equipment
Transmission													881.5	858.8
Other Property, Plant and Equipment													308.3	287.4
Construction Work in Progress													85.7	111.3
Total Property, Plant and Equipment													5,394.9	5,279.8
Accumulated Depreciation and Amortization													1,461.2	1,393.6
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													3,933.7	3,886.2
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													410.0	416.8
TOTAL ASSETS													4,513.5	4,508.3
Liabilities, Current [Abstract]
Accounts Payable													113.0	102.4
Affiliated Companies													42.2	48.0
Accrued Taxes													40.5	22.6
TOTAL CURRENT LIABILITIES													386.3	436.0
Noncurrent Liabilities
Deferred Income Taxes													636.6	642.0
Regulatory Liabilities and Deferred Investment Tax Credits													850.3	853.5
TOTAL NONCURRENT LIABILITIES													2,859.8	2,857.0
TOTAL LIABILITIES													3,246.1	3,293.0
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													4,513.5	4,508.3
Operating Activities
Net Income (Loss)		60.4		46.2		89.8		71.4
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		42.3		31.7		120.5		97.8
Deferred Income Taxes						(13.4)		93.7
Allowance for Equity Funds Used During Construction						0.3		(0.4)
Property Taxes						(9.6)		(9.4)
Change in Other Noncurrent Assets						6.9		(19.8)
Change in Other Noncurrent Liabilities						10.9		(1.4)
Accounts Receivable, Net						(3.4)		5.8
Fuel, Materials and Supplies						(1.5)		13.5
Accounts Payable						6.9		(18.5)
Accrued Taxes, Net						38.4		20.1
Other Current Assets						0.3		(8.2)
Other Current Liabilities						15.1		1.5
Net Cash Flows from (Used for) Operating Activities						326.7		191.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(158.9)		(201.6)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						(167.5)		10.3
Net Increase (Decrease) in Cash and Cash Equivalents						0.3		0.6
Cash and Cash Equivalents at Beginning of Period						1.6		1.5
Cash and Cash Equivalents at End of Period		1.9		2.1		1.9		2.1			2.1
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						42.0		40.9
Net Cash Paid (Received) for Income Taxes						1.6		(46.6)
Construction Expenditures Included in Current Liabilities as of September 30,						24.3		15.1
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		1.9		2.1		1.6		1.5			2.1		1.9	1.6	2.1	1.5
Southwestern Electric Power Co [Member]
Amounts Attributable to AEP Common Shareholders
Net Income Attributable to Noncontrolling Interests		1.4		11.0		4.1		12.6
Net Income (Loss) Available to Common Stockholders, Basic		88.2		73.1		137.6		113.9
Weighted Average Dilutive Effect of:
Income (Loss) from Equity Method Investments Adjustment						6.3
Net Income (Loss)		89.6		84.1		141.7		126.5
Retained Earnings (Accumulated Deficit)													1,503.8	1,426.6
Revenues
TOTAL REVENUES		535.3		517.6		1,411.8		1,343.6
Expenses
Depreciation and Amortization		59.9		55.2		175.9		158.1
TOTAL EXPENSES		408.2		381.6		1,172.6		1,080.7
OPERATING INCOME (LOSS)		127.1		136.0		239.2		262.9
Other Income (Expense):
Allowance for Equity Funds Used During Construction		0.6		0.4		3.8		1.2
Interest Expense		(32.7)		(31.9)		(95.8)		(92.7)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		98.4		106.2		157.6		176.2
Income Tax Expense (Credit)		9.6		22.5		17.9		45.2
Net Income (Loss)		89.6		84.1		141.7		126.5
Accounts Receivable:
Customers													29.1	70.9
Total Accounts Receivable													81.9	125.6
TOTAL CURRENT ASSETS													842.5	380.4
Property, Plant and Equipment
Transmission													1,812.0	1,679.8
Other Property, Plant and Equipment													744.4	684.1
Construction Work in Progress													234.5	233.2
Total Property, Plant and Equipment													9,592.9	9,317.8
Accumulated Depreciation and Amortization													2,798.9	2,685.8
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET													6,794.0	6,632.0
Other Noncurrent Assets
TOTAL OTHER NONCURRENT ASSETS													350.9	330.5
TOTAL ASSETS													7,987.4	7,342.9
Liabilities, Current [Abstract]
Accounts Payable													117.6	160.4
Affiliated Companies													41.3	63.7
Accrued Taxes													75.2	39.0
TOTAL CURRENT LIABILITIES													913.5	598.6
Noncurrent Liabilities
Deferred Income Taxes													932.9	917.7
Regulatory Liabilities and Deferred Investment Tax Credits													896.7	896.4
TOTAL NONCURRENT LIABILITIES													4,759.6	4,509.8
TOTAL LIABILITIES													5,673.1	5,108.4
Equity [Abstract]
TOTAL LIABILITIES AND EQUITY													7,987.4	7,342.9
Operating Activities
Net Income (Loss)		89.6		84.1		141.7		126.5
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization		59.9		55.2		175.9		158.1
Deferred Income Taxes						2.0		79.8
Allowance for Equity Funds Used During Construction		(0.6)		(0.4)		(3.8)		(1.2)
Property Taxes						(15.8)		(15.4)
Change in Other Noncurrent Assets						(8.9)		(2.9)
Change in Other Noncurrent Liabilities						52.1		(5.2)
Accounts Receivable, Net						44.3		12.1
Fuel, Materials and Supplies						5.0		13.6
Accounts Payable						(29.9)		(25.7)
Accrued Taxes, Net						38.4		69.1
Accrued Interest						(11.4)		(20.0)
Other Current Assets						3.2		0.7
Other Current Liabilities						15.6		(14.6)
Net Cash Flows from (Used for) Operating Activities						415.3		355.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(852.0)		(94.4)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						437.6		(269.6)
Net Increase (Decrease) in Cash and Cash Equivalents						0.9		(8.1)
Cash and Cash Equivalents at Beginning of Period						1.6		10.3
Cash and Cash Equivalents at End of Period		2.5		2.2		2.5		2.2			2.2
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						102.5		109.4
Net Cash Paid (Received) for Income Taxes						12.9		(70.5)
Construction Expenditures Included in Current Liabilities as of September 30,						37.0		40.7
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents		$ 2.5		$ 2.2		$ 1.6		$ 10.3			2.2		$ 2.5	1.6	2.2	10.3
Restricted Stock Units and Performance Share Units [Member]
Weighted Average Dilutive Effect of:
Weighted Average Dilutive Effect of Shares		900,000		1,200,000		900,000		600,000
Dilutive Securities, Effect on Basic Earnings Per Share		$ (0.00)		$ (0.01)		$ (0.01)		$ (0.00)
Previously Reported [Member] | AEP Transmission Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)				$ 59.9				$ 224.3
Retained Earnings (Accumulated Deficit)														788.7
Revenues
TOTAL REVENUES				167.3				549.4
Expenses
Depreciation and Amortization				24.8				70.9
TOTAL EXPENSES				72.2				198.5
OPERATING INCOME (LOSS)				95.1				350.9
Other Income (Expense):
Allowance for Equity Funds Used During Construction				11.7				36.0
Interest Expense				(16.9)				(48.6)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS				90.1				338.8
Income Tax Expense (Credit)				30.2				114.5
Net Income (Loss)				59.9				224.3
Accounts Receivable:
Customers														19.1
Total Accounts Receivable														113.6
Accrued Tax Benefits														46.6
TOTAL CURRENT ASSETS														327.7
Property, Plant and Equipment
Transmission														5,336.1
Other Property, Plant and Equipment														131.4
Construction Work in Progress														1,312.7
Total Property, Plant and Equipment														6,780.2
Accumulated Depreciation and Amortization														170.4
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET														6,609.8
Other Noncurrent Assets
Deferred Property Taxes														117.8
TOTAL OTHER NONCURRENT ASSETS														130.6
TOTAL ASSETS														7,068.1
Liabilities, Current [Abstract]
Accounts Payable														473.2
Affiliated Companies														52.9
Accrued Taxes														225.4
TOTAL CURRENT LIABILITIES														836.3
Noncurrent Liabilities
Deferred Income Taxes														601.7
Regulatory Liabilities and Deferred Investment Tax Credits														493.7
TOTAL NONCURRENT LIABILITIES														3,626.5
TOTAL LIABILITIES														4,462.8
Equity [Abstract]
TOTAL MEMBER'S EQUITY														2,605.3
TOTAL LIABILITIES AND EQUITY														7,068.1
Operating Activities
Net Income (Loss)				59.9				224.3
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization				24.8				70.9
Deferred Income Taxes								193.0
Allowance for Equity Funds Used During Construction				(11.7)				(36.0)
Change in Other Noncurrent Assets								7.6
Accounts Receivable, Net								(44.4)
Accounts Payable								8.6
Accrued Taxes, Net								(66.0)
Net Cash Flows from (Used for) Operating Activities								444.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities								(1,277.4)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities								832.5
Net Increase (Decrease) in Cash and Cash Equivalents								0.0
Cash and Cash Equivalents at Beginning of Period								0.0
Cash and Cash Equivalents at End of Period				0.0				0.0			0.0
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts								28.6
Construction Expenditures Included in Current Liabilities as of September 30,								239.0
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents				0.0				0.0			$ 0.0				0.0	0.0
Revision [Member] | AEP Transmission Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)				(1.3)				(11.9)
Retained Earnings (Accumulated Deficit)														(15.4)
Error Corrections and Prior Period Adjustments, Description										AEPTCo recorded a pretax out of period correction of an error of approximately $17 million related to revenue recorded from 2013 through March 31, 2018 in the second quarter of 2018	The $(18) million adjustment to pretax income for the nine months ended September 30, 2017 includes adjustments of $(12) million relating to 2016 and earlier periods. The effect of recording this adjustment of $(12) million in 2017 is not material to AEPTCo’s financial statements for 2017 or any earlier period.	The impact of this misstatement reduced AEPTCo’s pretax income by approximately $7 million on a cumulative basis for the period 2011 through June 30, 2018
Revenues
TOTAL REVENUES				(1.7)				(14.6)
Expenses
Depreciation and Amortization				(0.2)				(1.2)
TOTAL EXPENSES				(0.2)				(1.2)
OPERATING INCOME (LOSS)				(1.5)				(13.4)
Other Income (Expense):
Allowance for Equity Funds Used During Construction				(0.3)				(3.0)
Interest Expense				(0.2)				(1.8)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS				(2.0)				(18.2)
Income Tax Expense (Credit)				(0.7)				(6.3)
Net Income (Loss)				(1.3)				(11.9)
Accounts Receivable:
Customers														(4.1)
Total Accounts Receivable														(4.1)
Accrued Tax Benefits														2.8
TOTAL CURRENT ASSETS														(1.3)
Property, Plant and Equipment
Transmission														(16.4)
Other Property, Plant and Equipment														(4.6)
Construction Work in Progress														11.3
Total Property, Plant and Equipment														(9.7)
Accumulated Depreciation and Amortization														(17.8)
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET														8.1
Other Noncurrent Assets
Deferred Property Taxes														7.2
TOTAL OTHER NONCURRENT ASSETS														7.2
TOTAL ASSETS														14.0
Liabilities, Current [Abstract]
Accounts Payable														11.3
Affiliated Companies														13.2
Accrued Taxes														6.1
TOTAL CURRENT LIABILITIES														30.6
Noncurrent Liabilities
Deferred Income Taxes														(1.3)
Regulatory Liabilities and Deferred Investment Tax Credits														0.1
TOTAL NONCURRENT LIABILITIES														(1.2)
TOTAL LIABILITIES														29.4
Equity [Abstract]
TOTAL MEMBER'S EQUITY														(15.4)
TOTAL LIABILITIES AND EQUITY														$ 14.0
Operating Activities
Net Income (Loss)				(1.3)				(11.9)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization				(0.2)				(1.2)
Deferred Income Taxes								(1.1)
Allowance for Equity Funds Used During Construction				0.3				3.0
Change in Other Noncurrent Assets								1.0
Accounts Receivable, Net								3.6
Accounts Payable								11.8
Accrued Taxes, Net								(5.2)
Net Cash Flows from (Used for) Operating Activities								0.0
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities								0.0
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities								0.0
Net Increase (Decrease) in Cash and Cash Equivalents								0.0
Cash and Cash Equivalents at Beginning of Period								0.0
Cash and Cash Equivalents at End of Period				0.0				0.0			$ 0.0
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts								1.8
Construction Expenditures Included in Current Liabilities as of September 30,								9.9
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents				$ 0.0				$ 0.0			$ 0.0				$ 0.0	$ 0.0

[1] The amounts presented reflect the revisions made to AEPTCo’s previously issued financial statements. For additional details on revisions made to AEPTCo’s financial statements, see Note 1- Significant Accounting Matters.

[2] The amounts presented reflect the revisions made to AEPTCo’s previously issued financial statements. For additional details on revisions made to AEPTCo’s financial statements, see Note 1- Significant Accounting Matters.