Significant Accounting Matters (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			63 Months Ended	90 Months Ended
	Mar. 31, 2019	Mar. 31, 2018		Mar. 31, 2018	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Amounts Attributable to AEP Common Shareholders
EARNINGS ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 572.8	$ 454.4
Weighted Average Number of Basic AEP Common Shares Outstanding	493,309,076	492,267,402
Total Basic Earnings Per Share Attributable to AEP Common Shareholders	$ 1.16	$ 0.92
Weighted Average Dilutive Effect of:
Weighted Average Number of Diluted AEP Common Shares Outstanding	494,484,144	493,127,300
Total Diluted Earnings Per Share Attributable to AEP Common Shareholders	$ 1.16	$ 0.92
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	$ 227.7					$ 227.7	$ 234.1
Restricted Cash						135.4	210.0
Total Cash, Cash Equivalents and Restricted Cash						363.1	444.1
Total Cash, Cash Equivalents and Restricted Cash						363.1	444.1	$ 316.5	$ 412.6
Revenues
TOTAL REVENUES	4,056.8	$ 4,048.3
Expenses
Depreciation and Amortization	605.8	539.7
TOTAL EXPENSES	3,268.4	3,342.3
OPERATING INCOME (LOSS)	788.4	706.0
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction	28.9	30.7
Interest Expense	(255.8)	(234.0)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	600.1	540.2
Income Tax Expense (Benefit)	44.5	102.0
NET INCOME (LOSS)	574.1	456.7
Operating Activities
NET INCOME (LOSS)	574.1	456.7
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization	605.8	539.7
Deferred Income Taxes	16.8	87.3
Allowance for Equity Funds Used During Construction	(28.9)	(30.7)
Change in Other Noncurrent Assets	(47.9)	(59.8)
Change in Other Noncurrent Liabilities	67.3	133.3
Accounts Receivable, Net	57.5	39.7
Accounts Payable	(152.6)	(129.3)
Accrued Taxes, Net	(77.0)	(74.3)
Net Cash Flows from (Used for) Operating Activities	808.3	802.2
Investing Activities
Net Cash Flows from (Used for) Investing Activities	(1,582.8)	(1,927.8)
Financing Activities
Net Cash Flows from (Used for) Financing Activities	693.5	1,029.5
Cash and Cash Equivalents at Beginning of Period	234.1
Cash and Cash Equivalents at End of Period	227.7
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid	$ 846.3	$ 799.9
Organization and Summary of Significant Accounting Policies (Textuals)
Antidilutive Shares Outstanding	0	0
NET INCOME (LOSS)	$ 574.1	$ 456.7
Retained Earnings						9,565.6	9,325.3
Restricted Stock Units and Performance Share Units [Member]
Weighted Average Dilutive Effect of:
Weighted Average Dilutive Effect of Shares	1,200,000	800,000
Dilutive Securities, Effect on Basic Earnings Per Share	$ 0	$ 0
AEP Transmission Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	$ 0.0	$ 0.0		$ 0.0		0.0	0.0	0.0	0.0
Revenues
TOTAL REVENUES	243.5	191.7	[1],[2]
Expenses
Depreciation and Amortization	40.3	30.3
TOTAL EXPENSES	101.9	80.6
OPERATING INCOME (LOSS)	141.6	111.1
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction	11.3	14.9
Interest Expense	(21.7)	(20.3)	[1]
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	131.9	106.1
Income Tax Expense (Benefit)	27.6	22.0	[1]
NET INCOME (LOSS)	104.3	84.1	[1]
Operating Activities
NET INCOME (LOSS)	104.3	84.1	[1]
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization	40.3	30.3
Deferred Income Taxes	14.5	15.5
Allowance for Equity Funds Used During Construction	(11.3)	(14.9)
Change in Other Noncurrent Assets	2.7	2.9
Change in Other Noncurrent Liabilities	2.2	23.9
Accounts Receivable, Net	(8.2)	(9.6)
Accounts Payable	11.4	(10.7)
Accrued Taxes, Net	(32.1)	(34.0)
Net Cash Flows from (Used for) Operating Activities	166.2	127.1
Investing Activities
Net Cash Flows from (Used for) Investing Activities	(343.8)	(458.4)
Financing Activities
Net Cash Flows from (Used for) Financing Activities	177.6	331.3
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
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid	261.1	213.8
Organization and Summary of Significant Accounting Policies (Textuals)
NET INCOME (LOSS)	104.3	84.1	[1]
Retained Earnings						1,193.5	1,089.2
AEP Texas Inc. [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	3.1					0.1	3.1
Restricted Cash						100.6	156.7
Total Cash, Cash Equivalents and Restricted Cash						100.7	159.8
Total Cash, Cash Equivalents and Restricted Cash						100.7	159.8	107.2	157.2
Revenues
TOTAL REVENUES	390.7	371.6
Expenses
Depreciation and Amortization	138.9	110.0
TOTAL EXPENSES	319.9	289.8
OPERATING INCOME (LOSS)	70.8	81.8
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction	1.8	5.5
Interest Expense	(37.4)	(35.0)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	38.4	55.9
Income Tax Expense (Benefit)	4.0	9.1
NET INCOME (LOSS)	34.4	46.8
Operating Activities
NET INCOME (LOSS)	34.4	46.8
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization	138.9	110.0
Deferred Income Taxes	(11.0)	(4.4)
Allowance for Equity Funds Used During Construction	(1.8)	(5.5)
Change in Other Noncurrent Assets	(3.2)	(12.7)
Change in Other Noncurrent Liabilities	(5.7)	6.5
Accounts Receivable, Net	(7.8)	1.8
Accounts Payable	4.2	(25.9)
Accrued Taxes, Net	57.5	25.2
Net Cash Flows from (Used for) Operating Activities	126.8	79.0
Investing Activities
Net Cash Flows from (Used for) Investing Activities	(336.6)	(364.4)
Financing Activities
Net Cash Flows from (Used for) Financing Activities	150.7	235.4
Cash and Cash Equivalents at Beginning of Period	3.1
Cash and Cash Equivalents at End of Period	0.1
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid	195.7	169.3
Organization and Summary of Significant Accounting Policies (Textuals)
NET INCOME (LOSS)	34.4	46.8
Retained Earnings						1,372.1	1,337.7
Appalachian Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	2.9					2.9	4.2
Restricted Cash						18.3	25.6
Total Cash, Cash Equivalents and Restricted Cash						21.2	29.8	11.3	19.2
Revenues
TOTAL REVENUES	792.8	820.4
Expenses
Depreciation and Amortization	112.5	108.5
TOTAL EXPENSES	640.7	627.4
OPERATING INCOME (LOSS)	152.1	193.0
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction	1.7	2.6
Interest Expense	(49.3)	(47.4)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	109.6	153.5
Income Tax Expense (Benefit)	(24.1)	28.0
NET INCOME (LOSS)	133.7	125.5
Operating Activities
NET INCOME (LOSS)	133.7	125.5
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization	112.5	108.5
Deferred Income Taxes	(45.0)	11.0
Allowance for Equity Funds Used During Construction	(1.7)	(2.6)
Change in Other Noncurrent Assets	(12.1)	3.9
Change in Other Noncurrent Liabilities	(20.5)	37.9
Accounts Receivable, Net	19.5	(14.2)
Accounts Payable	(8.3)	(21.6)
Accrued Taxes, Net	13.7	17.8
Net Cash Flows from (Used for) Operating Activities	250.5	199.5
Investing Activities
Net Cash Flows from (Used for) Investing Activities	(383.5)	(214.1)
Financing Activities
Net Cash Flows from (Used for) Financing Activities	124.4	6.7
Cash and Cash Equivalents at Beginning of Period	4.2
Cash and Cash Equivalents at End of Period	2.9
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid	87.8	94.5
Organization and Summary of Significant Accounting Policies (Textuals)
NET INCOME (LOSS)	133.7	125.5
Retained Earnings						2,005.7	1,922.0
Ohio Power Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents	3.3					3.3	4.9
Restricted Cash						16.5	27.6
Total Cash, Cash Equivalents and Restricted Cash						19.8	32.5	17.3	29.7
Revenues
TOTAL REVENUES	836.8	790.9
Expenses
Depreciation and Amortization	63.3	64.8
TOTAL EXPENSES	674.3	673.6
OPERATING INCOME (LOSS)	162.5	117.3
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction	5.2	2.5
Interest Expense	(24.6)	(25.2)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS	147.8	100.1
Income Tax Expense (Benefit)	19.8	20.5
NET INCOME (LOSS)	128.0	79.6
Operating Activities
NET INCOME (LOSS)	128.0	79.6
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization	63.3	64.8
Deferred Income Taxes	10.1	(4.9)
Allowance for Equity Funds Used During Construction	(5.2)	(2.5)
Change in Other Noncurrent Assets	(7.3)	14.3
Change in Other Noncurrent Liabilities	17.6	40.6
Accounts Receivable, Net	31.7	38.8
Accounts Payable	(23.9)	(22.5)
Accrued Taxes, Net	(114.4)	(92.8)
Net Cash Flows from (Used for) Operating Activities	117.2	184.8
Investing Activities
Net Cash Flows from (Used for) Investing Activities	(194.8)	(366.9)
Financing Activities
Net Cash Flows from (Used for) Financing Activities	64.9	169.7
Cash and Cash Equivalents at Beginning of Period	4.9
Cash and Cash Equivalents at End of Period	3.3
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid	72.8	52.3
Organization and Summary of Significant Accounting Policies (Textuals)
NET INCOME (LOSS)	$ 128.0	79.6
Retained Earnings						$ 1,239.4	$ 1,136.4
Previously Reported [Member] | AEP Transmission Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		0.0		0.0				0.0	0.0
Revenues
TOTAL REVENUES		193.5
Expenses
Depreciation and Amortization		30.6
TOTAL EXPENSES		80.9
OPERATING INCOME (LOSS)		112.6
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction		15.3
Interest Expense		(19.9)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		108.4
Income Tax Expense (Benefit)		22.5
NET INCOME (LOSS)		85.9
Operating Activities
NET INCOME (LOSS)		85.9
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization		30.6
Deferred Income Taxes		15.7
Allowance for Equity Funds Used During Construction		(15.3)
Change in Other Noncurrent Assets		2.7
Accounts Receivable, Net		(10.1)
Accounts Payable		(12.3)
Accrued Taxes, Net		(33.6)
Net Cash Flows from (Used for) Operating Activities		127.1
Investing Activities
Net Cash Flows from (Used for) Investing Activities		(458.4)
Financing Activities
Net Cash Flows from (Used for) Financing Activities		331.3
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
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid		210.6
Organization and Summary of Significant Accounting Policies (Textuals)
NET INCOME (LOSS)		85.9
Revision [Member] | AEP Transmission Co [Member]
Cash, Cash Equivalents and Restricted Cash
Cash and Cash Equivalents		0.0		0.0				$ 0.0	0.0
Revenues
TOTAL REVENUES		(1.8)
Expenses
Depreciation and Amortization		(0.3)
TOTAL EXPENSES		(0.3)
OPERATING INCOME (LOSS)		(1.5)
Nonoperating Income (Expense)
Allowance for Equity Funds Used During Construction		(0.4)
Interest Expense		(0.4)
INCOME BEFORE INCOME TAX EXPENSE AND EQUITY EARNINGS		(2.3)
Income Tax Expense (Benefit)		(0.5)
NET INCOME (LOSS)		(1.8)
Operating Activities
NET INCOME (LOSS)		(1.8)
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities
Utilities Operating Expense, Depreciation and Amortization		(0.3)
Deferred Income Taxes		(0.2)
Allowance for Equity Funds Used During Construction		0.4
Change in Other Noncurrent Assets		0.2
Accounts Receivable, Net		0.5
Accounts Payable		1.6
Accrued Taxes, Net		(0.4)
Net Cash Flows from (Used for) Operating Activities		0.0
Investing Activities
Net Cash Flows from (Used for) Investing Activities		0.0
Financing Activities
Net Cash Flows from (Used for) 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
Supplementary Information
Construction in Progress Expenditures Incurred but Not yet Paid		3.2
Organization and Summary of Significant Accounting Policies (Textuals)
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
NET INCOME (LOSS)		$ (1.8)
Retained Earnings									$ (15.0)

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