Significant Accounting Matters (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended					6 Months Ended			63 Months Ended	90 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018		Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018		Mar. 31, 2018	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Amounts Attributable to AEP Common Shareholders
Earnings Attributable to Common Shareholders	$ 461.3		$ 528.4			$ 1,034.1	$ 982.8
Weighted Average Number of Basic AEP Common Shares Outstanding	493,584,347		492,688,342			493,447,477	492,479,035
Total Basic Earnings Per Share Attributable to AEP Common Shareholders	$ 0.93		$ 1.07			$ 2.10	$ 2.00
Weighted Average Dilutive Effect of:
Weighted Average Number of Diluted AEP Common Shares Outstanding	495,382,966		493,505,085			494,934,320	493,317,355
Total Diluted Earnings Per Share Attributable to AEP Common Shareholders	$ 0.93		$ 1.07			$ 2.09	$ 1.99
Antidilutive Shares Outstanding						0	0
Net Income (Loss)	$ 459.1	$ 574.1	$ 530.1		$ 456.7	$ 1,033.2	$ 986.8
Retained Earnings (Accumulated Deficit)											$ 9,694.2	$ 9,325.3
Revenues
TOTAL REVENUES	3,573.6		4,013.2			7,630.4	8,061.5
Expenses
Depreciation and Amortization	622.6		553.2			1,228.4	1,092.9
TOTAL EXPENSES	3,022.6		3,256.2			6,291.0	6,598.5
OPERATING INCOME (LOSS)	551.0		757.0			1,339.4	1,463.0
Other Income (Expense):
Allowance for Equity Funds Used During Construction	50.4		30.8			79.3	61.5
Interest Expense	(250.7)		(242.3)			(506.5)	(476.3)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	387.3		583.6			987.4	1,123.8
Income Tax Expense (Benefit)	(54.4)		72.2			(9.9)	174.2
Net Income (Loss)	459.1	574.1	530.1		456.7	1,033.2	986.8
Operating Activities
Net Income (Loss)	459.1	574.1	530.1		456.7	1,033.2	986.8
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	622.6		553.2			1,228.4	1,092.9
Deferred Income Taxes						(35.5)	149.7
Allowance for Equity Funds Used During Construction	(50.4)		(30.8)			(79.3)	(61.5)
Property Taxes						137.6	119.9
Change in Other Noncurrent Assets						(73.5)	10.4
Change in Other Noncurrent Liabilities						(53.6)	185.1
Accounts Receivable, Net						165.5	(209.9)
Fuel, Materials and Supplies						(114.6)	31.2
Accounts Payable						(72.4)	(53.6)
Accrued Taxes, Net						(170.1)	(127.8)
Other Current Assets						27.4	14.8
Other Current Liabilities						(223.0)	(112.3)
Net Cash Flows from (Used for) Operating Activities						1,800.8	2,006.8
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(3,595.0)	(3,238.9)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						1,739.7	1,206.8
Cash and Cash Equivalents at Beginning of Period		234.1				234.1
Cash and Cash Equivalents at End of Period	210.5					210.5
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						490.2	455.4
Net Cash Paid (Received) for Income Taxes						19.7	33.8
Construction Expenditures Included in Current Liabilities as of June 30,						904.8	940.0
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	210.5	234.1				210.5					210.5	234.1
Restricted Cash											179.1	210.0
Total Cash, Cash Equivalents and Restricted Cash											389.6	444.1
Total Cash, Cash Equivalents and Restricted Cash											389.6	444.1	$ 387.3	$ 412.6
AEP Texas Inc. [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)	80.6	34.4	46.5		46.8	115.0	93.3
Retained Earnings (Accumulated Deficit)											1,452.7	1,337.7
Revenues
TOTAL REVENUES	438.0		388.3			828.7	759.9
Expenses
Depreciation and Amortization	155.7		121.6			294.6	231.6
TOTAL EXPENSES	399.3		302.1			719.2	591.9
OPERATING INCOME (LOSS)	38.7		86.2			109.5	168.0
Other Income (Expense):
Allowance for Equity Funds Used During Construction						3.2	9.4
Interest Expense	(19.5)		(36.6)			(56.9)	(71.6)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	24.1		55.5			62.5	111.4
Income Tax Expense (Benefit)	(56.5)		9.0			(52.5)	18.1
Net Income (Loss)	80.6	34.4	46.5		46.8	115.0	93.3
Operating Activities
Net Income (Loss)	80.6	34.4	46.5		46.8	115.0	93.3
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	155.7		121.6			294.6	231.6
Deferred Income Taxes						(59.9)	24.9
Allowance for Equity Funds Used During Construction						(3.2)	(9.4)
Property Taxes						(45.0)	(38.4)
Change in Other Noncurrent Assets						24.4	(36.1)
Change in Other Noncurrent Liabilities						5.6	21.6
Accounts Receivable, Net						(46.2)	(67.1)
Fuel, Materials and Supplies						0.8	0.5
Accounts Payable						1.8	(29.6)
Accrued Taxes, Net						26.4	37.5
Other Current Assets						2.0	1.6
Other Current Liabilities						(21.8)	(5.5)
Net Cash Flows from (Used for) Operating Activities						294.5	224.9
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(663.7)	(688.8)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						334.9	438.7
Cash and Cash Equivalents at Beginning of Period		3.1				3.1
Cash and Cash Equivalents at End of Period	0.1					0.1
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						73.4	69.3
Net Cash Paid (Received) for Income Taxes						14.4	(22.4)
Construction Expenditures Included in Current Liabilities as of June 30,						192.9	186.8
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	0.1	3.1				0.1					0.1	3.1
Restricted Cash											125.4	156.7
Total Cash, Cash Equivalents and Restricted Cash											125.5	159.8
Total Cash, Cash Equivalents and Restricted Cash											125.5	159.8	132.0	157.2
AEP Transmission Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)	136.0	104.3	82.0		84.1	240.3	166.1
Retained Earnings (Accumulated Deficit)											1,329.5	1,089.2
Revenues
TOTAL REVENUES	266.9		200.1	[1]		510.4	391.8	[2]
Expenses
Depreciation and Amortization	42.8		32.3			83.1	62.6
TOTAL EXPENSES	105.9		89.6			207.8	170.2
OPERATING INCOME (LOSS)	161.0		110.5			302.6	221.6
Other Income (Expense):
Allowance for Equity Funds Used During Construction	28.8		15.8			40.1	30.7
Interest Expense	(21.4)		(20.6)			(43.1)	(40.9)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	169.0		106.1			300.9	212.2
Income Tax Expense (Benefit)	33.0		24.1			60.6	46.1
Net Income (Loss)	136.0	104.3	82.0		84.1	240.3	166.1
Operating Activities
Net Income (Loss)	136.0	104.3	82.0		84.1	240.3	166.1
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	42.8		32.3			83.1	62.6
Deferred Income Taxes						19.7	49.9
Allowance for Equity Funds Used During Construction	(28.8)		(15.8)			(40.1)	(30.7)
Property Taxes						68.3	44.7
Long-term Accounts Receivable - Affiliated						(7.8)	(6.2)
Change in Other Noncurrent Assets						3.6	(6.7)
Change in Other Noncurrent Liabilities						(6.4)	17.8
Accounts Receivable, Net						(31.7)	8.5
Fuel, Materials and Supplies						1.8	(2.4)
Accounts Payable						6.3	3.4
Accrued Taxes, Net						(43.1)	(29.8)
Accrued Interest						0.4	(3.3)
Other Current Assets						0.0	0.4
Other Current Liabilities						(0.2)	(28.2)
Net Cash Flows from (Used for) Operating Activities						294.2	246.1
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(613.6)	(774.7)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						319.4	528.6
Net Increase (Decrease) in Cash and Cash Equivalents						0.0	0.0
Cash and Cash Equivalents at Beginning of Period		0.0			0.0	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						41.0	43.1
Net Cash Paid (Received) for Income Taxes						17.4	(20.4)
Construction Expenditures Included in Current Liabilities as of June 30,						278.5	241.1
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	0.0	0.0
Appalachian Power Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)	55.5	133.7	77.4		125.5	189.2	202.9
Retained Earnings (Accumulated Deficit)											2,011.2	1,922.0
Revenues
TOTAL REVENUES	655.8		667.0			1,448.6	1,487.4
Expenses
Depreciation and Amortization	117.1		105.3			229.6	213.8
TOTAL EXPENSES	578.9		534.4			1,219.6	1,161.8
OPERATING INCOME (LOSS)	76.9		132.6			229.0	325.6
Other Income (Expense):
Allowance for Equity Funds Used During Construction	6.0		2.9			7.7	5.5
Interest Expense	(51.6)		(47.8)			(100.9)	(95.2)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	36.5		93.2			146.1	246.7
Income Tax Expense (Benefit)	(19.0)		15.8			(43.1)	43.8
Net Income (Loss)	55.5	133.7	77.4		125.5	189.2	202.9
Operating Activities
Net Income (Loss)	55.5	133.7	77.4		125.5	189.2	202.9
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	117.1		105.3			229.6	213.8
Deferred Income Taxes						(73.5)	10.8
Allowance for Equity Funds Used During Construction	(6.0)		(2.9)			(7.7)	(5.5)
Change in Other Noncurrent Assets						(1.8)	32.0
Change in Other Noncurrent Liabilities						(31.2)	68.7
Accounts Receivable, Net						60.2	4.7
Fuel, Materials and Supplies						(50.2)	20.2
Accounts Payable						23.0	(11.1)
Accrued Taxes, Net						(7.8)	(7.6)
Other Current Assets						17.4	7.1
Other Current Liabilities						(29.8)	(21.9)
Net Cash Flows from (Used for) Operating Activities						345.9	404.2
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(376.1)	(398.9)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						28.1	(4.0)
Cash and Cash Equivalents at Beginning of Period		4.2				4.2
Cash and Cash Equivalents at End of Period	2.3					2.3
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						91.6	90.9
Net Cash Paid (Received) for Income Taxes						35.0	19.7
Construction Expenditures Included in Current Liabilities as of June 30,						116.5	89.5
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	2.3	4.2				2.3					2.3	4.2
Restricted Cash											25.4	25.6
Total Cash, Cash Equivalents and Restricted Cash											27.7	29.8	20.5	19.2
Indiana Michigan Power Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)	60.3	98.9	94.7		64.2	159.2	158.9
Retained Earnings (Accumulated Deficit)											1,448.3	1,329.1
Revenues
TOTAL REVENUES	543.1		589.7			1,157.4	1,166.5
Expenses
Depreciation and Amortization	87.3		62.6			173.5	121.9
TOTAL EXPENSES	465.2		472.3			964.5	951.7
OPERATING INCOME (LOSS)	77.9		117.4			192.9	214.8
Other Income (Expense):
Allowance for Equity Funds Used During Construction						12.5	4.1
Interest Expense	(28.2)		(31.4)			(57.1)	(61.1)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	60.2		95.4			156.4	172.0
Income Tax Expense (Benefit)	(0.1)		0.7			(2.8)	13.1
Net Income (Loss)	60.3	98.9	94.7		64.2	159.2	158.9
Operating Activities
Net Income (Loss)	60.3	98.9	94.7		64.2	159.2	158.9
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	87.3		62.6			173.5	121.9
Deferred Income Taxes						(17.2)	33.1
Allowance for Equity Funds Used During Construction						(12.5)	(4.1)
Change in Other Noncurrent Assets						32.6	(5.6)
Change in Other Noncurrent Liabilities						(3.6)	44.4
Accounts Receivable, Net						35.8	(18.3)
Fuel, Materials and Supplies						(3.8)	(5.0)
Accounts Payable						(50.4)	(12.2)
Accrued Taxes, Net						(15.9)	0.8
Other Current Assets						9.6	1.2
Other Current Liabilities						(38.6)	(16.9)
Net Cash Flows from (Used for) Operating Activities						279.4	345.0
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(346.0)	(410.6)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						65.6	65.7
Net Increase (Decrease) in Cash and Cash Equivalents						(1.0)	0.1
Cash and Cash Equivalents at Beginning of Period		2.4			1.3	2.4	1.3
Cash and Cash Equivalents at End of Period	1.4		1.4			1.4	1.4			1.4
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						55.2	55.2
Net Cash Paid (Received) for Income Taxes						27.9	(23.6)
Construction Expenditures Included in Current Liabilities as of June 30,						77.7	86.5
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	1.4	2.4	1.4		1.3	2.4	1.3			1.4	1.4	2.4	1.4	1.3
Ohio Power Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)	50.6	128.0	68.8		79.6	178.6	148.4
Retained Earnings (Accumulated Deficit)											1,230.0	1,136.4
Revenues
TOTAL REVENUES	606.6		748.8			1,443.4	1,539.7
Expenses
Depreciation and Amortization	56.1		65.1			119.4	129.9
TOTAL EXPENSES	529.5		644.4			1,203.8	1,318.0
OPERATING INCOME (LOSS)	77.1		104.4			239.6	221.7
Other Income (Expense):
Allowance for Equity Funds Used During Construction	4.1		3.3			9.3	5.8
Interest Expense	(25.6)		(25.3)			(50.2)	(50.5)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	60.5		87.8			208.3	187.9
Income Tax Expense (Benefit)	9.9		19.0			29.7	39.5
Net Income (Loss)	50.6	128.0	68.8		79.6	178.6	148.4
Operating Activities
Net Income (Loss)	50.6	128.0	68.8		79.6	178.6	148.4
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	56.1		65.1			119.4	129.9
Deferred Income Taxes						9.4	(12.5)
Allowance for Equity Funds Used During Construction	(4.1)		(3.3)			(9.3)	(5.8)
Property Taxes						130.1	129.6
Change in Other Noncurrent Assets						(30.1)	83.3
Change in Other Noncurrent Liabilities						(38.0)	56.0
Accounts Receivable, Net						70.0	14.0
Fuel, Materials and Supplies						(8.5)	(3.6)
Accounts Payable						(34.9)	(39.9)
Accrued Taxes, Net						(169.4)	(169.5)
Other Current Assets						(4.2)	(0.6)
Other Current Liabilities						2.6	(11.4)
Net Cash Flows from (Used for) Operating Activities						219.5	380.6
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(441.9)	(300.1)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						220.8	(80.4)
Cash and Cash Equivalents at Beginning of Period		4.9				4.9
Cash and Cash Equivalents at End of Period	2.7					2.7
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						46.1	48.3
Net Cash Paid (Received) for Income Taxes						14.3	45.1
Construction Expenditures Included in Current Liabilities as of June 30,						77.9	64.5
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	2.7	4.9				2.7					2.7	4.9
Restricted Cash											28.2	27.6
Total Cash, Cash Equivalents and Restricted Cash											30.9	32.5	29.8	29.7
Public Service Co Of Oklahoma [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)	41.9	6.2	36.6		(7.2)	48.1	29.4
Retained Earnings (Accumulated Deficit)											761.5	724.7
Revenues
TOTAL REVENUES	348.1		398.3			680.9	735.1
Expenses
Depreciation and Amortization	42.8		41.4			86.3	78.2
TOTAL EXPENSES	291.5		341.1			603.4	674.0
OPERATING INCOME (LOSS)	56.6		57.2			77.5	61.1
Other Income (Expense):
Allowance for Equity Funds Used During Construction						0.7	(0.1)
Interest Expense	(17.3)		(16.3)			(34.2)	(31.0)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	42.2		43.0			48.4	34.4
Income Tax Expense (Benefit)	0.3		6.4			0.3	5.0
Net Income (Loss)	41.9	6.2	36.6		(7.2)	48.1	29.4
Operating Activities
Net Income (Loss)	41.9	6.2	36.6		(7.2)	48.1	29.4
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	42.8		41.4			86.3	78.2
Deferred Income Taxes						(9.0)	(6.5)
Allowance for Equity Funds Used During Construction						(0.7)	0.1
Property Taxes						(19.2)	(19.2)
Change in Other Noncurrent Assets						4.6	1.4
Change in Other Noncurrent Liabilities						(2.4)	14.8
Accounts Receivable, Net						(12.6)	(6.4)
Fuel, Materials and Supplies						0.4	(0.8)
Accounts Payable						28.5	23.0
Accrued Taxes, Net						12.8	30.0
Other Current Assets						(1.6)	0.5
Other Current Liabilities						3.3	3.0
Net Cash Flows from (Used for) Operating Activities						129.2	159.3
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(131.6)	(101.5)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						1.8	(57.8)
Net Increase (Decrease) in Cash and Cash Equivalents						(0.6)	0.0
Cash and Cash Equivalents at Beginning of Period		2.0			1.6	2.0	1.6
Cash and Cash Equivalents at End of Period	1.4		1.6			1.4	1.6			1.6
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						30.9	31.7
Net Cash Paid (Received) for Income Taxes						11.1	(1.8)
Construction Expenditures Included in Current Liabilities as of June 30,						19.7	25.9
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	1.4	2.0	1.6		1.6	1.4	1.6			1.6	1.4	2.0	1.6	1.6
Southwestern Electric Power Co [Member]
Amounts Attributable to AEP Common Shareholders
Earnings Attributable to Common Shareholders	6.2		37.6			34.0	49.4
Weighted Average Dilutive Effect of:
Income (Loss) from Equity Method Investments Adjustment						6.3
Net Income (Loss)	7.3	29.0	38.7		13.4	36.3	52.1
Retained Earnings (Accumulated Deficit)											1,504.9	1,508.4
Revenues
TOTAL REVENUES	375.5		457.1			796.6	876.5
Expenses
Depreciation and Amortization	61.8		58.6			123.9	116.0
TOTAL EXPENSES	342.5		386.6			709.5	764.4
OPERATING INCOME (LOSS)	33.0		70.5			87.1	112.1
Other Income (Expense):
Allowance for Equity Funds Used During Construction	1.1		0.9			2.9	3.2
Interest Expense	(30.5)		(30.9)			(60.2)	(63.1)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	6.5		43.4			35.5	59.2
Income Tax Expense (Benefit)	0.0		5.4			0.7	8.3
Net Income (Loss)	7.3	29.0	38.7		13.4	36.3	52.1
Operating Activities
Net Income (Loss)	7.3	29.0	38.7		13.4	36.3	52.1
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization	61.8		58.6			123.9	116.0
Deferred Income Taxes						(10.1)	0.4
Allowance for Equity Funds Used During Construction	(1.1)		(0.9)			(2.9)	(3.2)
Property Taxes						(32.2)	(31.6)
Change in Other Noncurrent Assets						2.9	(7.6)
Change in Other Noncurrent Liabilities						2.0	45.4
Accounts Receivable, Net						(26.1)	22.1
Fuel, Materials and Supplies						(19.3)	1.2
Accounts Payable						5.5	(17.3)
Accrued Taxes, Net						47.7	31.8
Other Current Assets						(1.4)	4.5
Other Current Liabilities						23.4	10.5
Net Cash Flows from (Used for) Operating Activities						151.7	226.2
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities						(106.0)	(244.0)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities						(46.2)	18.3
Net Increase (Decrease) in Cash and Cash Equivalents						(0.5)	0.5
Cash and Cash Equivalents at Beginning of Period		24.5			1.6	24.5	1.6
Cash and Cash Equivalents at End of Period	24.0		2.1			24.0	2.1			2.1
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts						57.1	59.7
Net Cash Paid (Received) for Income Taxes						6.2	16.3
Construction Expenditures Included in Current Liabilities as of June 30,						40.9	39.5
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents	$ 24.0	$ 24.5	$ 2.1		1.6	$ 24.5	$ 1.6			2.1	$ 24.0	$ 24.5	2.1	1.6
Restricted Stock Units and Performance Share Units [Member]
Weighted Average Dilutive Effect of:
Weighted Average Dilutive Effect of Shares	1,800,000		800,000			1,500,000	800,000
Dilutive Securities, Effect on Basic Earnings Per Share	$ 0		$ 0			$ (0.01)	$ (0.01)
Previously Reported [Member] | AEP Transmission Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)			$ 70.5				$ 156.4
Revenues
TOTAL REVENUES			183.8				377.3
Expenses
Depreciation and Amortization			32.4				63.0
TOTAL EXPENSES			89.7				170.6
OPERATING INCOME (LOSS)			94.1				206.7
Other Income (Expense):
Allowance for Equity Funds Used During Construction			16.3				31.6
Interest Expense			(20.3)				(40.2)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS			90.5				198.9
Income Tax Expense (Benefit)			20.0				42.5
Net Income (Loss)			70.5				156.4
Operating Activities
Net Income (Loss)			70.5				156.4
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization			32.4				63.0
Deferred Income Taxes							50.2
Allowance for Equity Funds Used During Construction			(16.3)				(31.6)
Change in Other Noncurrent Assets							(7.0)
Accounts Receivable, Net							8.4
Accounts Payable							13.7
Net Cash Flows from (Used for) Operating Activities							246.1
Net Cash Provided by (Used in) Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities							(774.7)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Net Cash Provided by (Used in) Financing Activities							528.6
Net Increase (Decrease) in Cash and Cash Equivalents							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
Supplementary Information [Abstract]
Cash Paid for Interest, Net of Capitalized Amounts							42.7
Construction Expenditures Included in Current Liabilities as of June 30,							234.7
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents			0.0		0.0		0.0			$ 0.0			0.0	0.0
Revision [Member] | AEP Transmission Co [Member]
Weighted Average Dilutive Effect of:
Net Income (Loss)			11.5				9.7
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 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			16.3				14.5
Expenses
Depreciation and Amortization			(0.1)				(0.4)
TOTAL EXPENSES			(0.1)				(0.4)
OPERATING INCOME (LOSS)			16.4				14.9
Other Income (Expense):
Allowance for Equity Funds Used During Construction			(0.5)				(0.9)
Interest Expense			(0.3)				(0.7)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS			15.6				13.3
Income Tax Expense (Benefit)			4.1				3.6
Net Income (Loss)			11.5				9.7
Operating Activities
Net Income (Loss)			11.5				9.7
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation and Amortization			(0.1)				(0.4)
Deferred Income Taxes							(0.3)
Allowance for Equity Funds Used During Construction			0.5				0.9
Change in Other Noncurrent Assets							0.3
Accounts Receivable, Net							0.1
Accounts Payable							(10.3)
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		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							0.4
Construction Expenditures Included in Current Liabilities as of June 30,							6.4
Cash, Cash Equivalents and Restricted Cash [Abstract]
Cash and Cash Equivalents			$ 0.0		$ 0.0		$ 0.0			$ 0.0			$ 0.0	$ 0.0

[1] These amounts presented reflect the revisions made to AEPTCo’s previously issued financial statement. See the “revisions to Previously Issued Financial Statements” section of Note 1 for additional information.

[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.