Financing Activities (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended
		Apr. 26, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Long-term Debt
Senior Unsecured Notes			$ 17,004.6		$ 16,478.3
Pollution Control Bonds			1,540.4		1,621.7
Notes Payable			230.2		260.8
Securitization Bonds			1,285.9		1,416.5
Spent Nuclear Fuel Obligation	[1]		269.5		268.6
Other Long-term Debt			1,130.4		1,127.4
Total Long-term Debt Outstanding			21,461.0		21,173.3
Long-term Debt Due Within One Year			2,616.1		1,753.7
Long-term Debt			18,844.9		19,419.6
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Issuances	[2]		853.4
Retirements and Principal Payments			544.0	$ 1,242.3
Short-term Debt:
Securitized Debt for Receivables	[3]		750.0		718.0
Commercial Paper			1,886.2		898.6
Notes Payable			22.6		22.0
Total Short-term Debt			$ 2,658.8		$ 1,638.6
Securitized Debt for Receivables	[3],[4]		1.74%		1.22%
Comparative Accounts Receivable Information
Effective Interest Rates on Securitization of Accounts Receivable			1.74%	1.00%
Net Uncollectible Accounts Receivable Written Off			$ 4.2	$ 5.9
Customer Accounts Receivable Managed Portfolio
Accounts Receivable Retained Interest and Pledged as Collateral Less Uncollectible Accounts			944.5		$ 925.5
Total Principal Outstanding			750.0		718.0
Delinquent Securitized Accounts Receivable			55.1		41.1
Bad Debt Reserves Related to Securitization of Accounts Receivable			30.8		28.7
Unbilled Receivables Related to Securitization of Accounts Receivable			249.9		303.2
Financing Activities (Textuals) [Abstract]
Trust Fund Assets One Time Fee Obligation for Nuclear Fuel Disposition			313.0		312.0
Reacquired Pollution Controls Bonds Held by Trustees			678.0
Repayments of Long-term Debt			544.0	1,242.3
Issuance of Long-term Debt	[2]		$ 853.4
Maximum Percentage Debt to Capitalization			67.50%
Total Commitment from Bank Conduits to Finance Receivables			$ 750.0
AEP Texas Inc. [Member]
Long-term Debt
Total Long-term Debt Outstanding			3,553.3		3,649.3
Long-term Debt Due Within One Year			273.1		266.1
Long-term Debt			3,280.2		3,383.2
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			96.5	89.9
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 96.5	$ 89.9
Maximum Percentage Debt to Capitalization			67.50%
AEP Texas Inc. [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 307.2
Maximum Loans to Money Pool			103.6
Average Borrowings from Money Pool			219.2
Average Loans to Money Pool			50.4
Net Loans (Borrowings) to/from Utility Money Pool			(232.7)
Authorized Short Term Borrowing Limit			$ 500.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.07%	1.02%
Average Interest Rate For Funds Loaned			1.90%	0.00%
AEP Texas Inc. [Member] | Nonutility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 0.0
Maximum Loans to Money Pool			8.4
Average Borrowings from Money Pool			0.0
Average Loans to Money Pool			8.2
Net Loans (Borrowings) to/from Utility Money Pool			$ 8.1
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate for Funds Borrowed			0.00%	0.00%
Minimum Interest Rate For Funds Borrowed			0.00%	0.00%
Maximum Interest Rate For Funds Loaned			2.42%	1.27%
Minimum Interest Rate for Funds Loaned			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			0.00%	0.00%
Average Interest Rate For Funds Loaned			2.00%	1.03%
AEP Texas Inc. [Member] | Securitization Bonds [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 70.0
Debt Instrument, Interest Rate, Stated Percentage			5.17%
Due Date			2018
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 70.0
Due Date			2018
AEP Texas Inc. [Member] | Securitization Bonds Two [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 26.5
Debt Instrument, Interest Rate, Stated Percentage			5.306%
Due Date			2020
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 26.5
Due Date			2020
AEP Texas Inc. [Member] | Senior Unsecured Notes [Member] | Subsequent Event [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments		$ 30.0
Debt Instrument, Interest Rate, Stated Percentage		5.89%
Due Date		2018
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt		$ 30.0
Due Date		2018
AEP Transmission Co [Member]
Long-term Debt
Total Long-term Debt Outstanding			$ 2,550.7		2,550.4
Long-term Debt Due Within One Year			50.0		50.0
Long-term Debt			2,500.7		2,500.4
Financing Activities (Textuals) [Abstract]
Sub-Limit of Secured Debt			$ 50.0
Maximum Percentage of Consolidated Tangible Net Assets			10.00%
Tangible Capital to Tangible Assets			4.50%
Maximum Percentage Debt to Capitalization			67.50%
AEP Transmission Co [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 337.3
Maximum Loans to Money Pool			123.9
Average Borrowings from Money Pool			188.2
Average Loans to Money Pool			26.3
Net Loans (Borrowings) to/from Utility Money Pool			(272.8)
Authorized Short Term Borrowing Limit	[5]		$ 795.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.06%	1.08%
Average Interest Rate For Funds Loaned			1.92%	0.99%
AEP Transmission Co [Member] | Direct Borrowing [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 1.1
Maximum Loans to Money Pool			104.7
Average Borrowings from Money Pool			1.1
Average Loans to Money Pool			51.1
Borrowings from Parent			1.1
Loans to Parent			23.9
Authorized Short Term Borrowing Limit	[6]		$ 75.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate for Funds Borrowed			2.42%	1.27%
Minimum Interest Rate For Funds Borrowed			1.83%	0.92%
Maximum Interest Rate For Funds Loaned			2.42%	1.27%
Minimum Interest Rate for Funds Loaned			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.00%	1.03%
Average Interest Rate For Funds Loaned			2.02%	1.04%
Appalachian Power Co [Member]
Long-term Debt
Total Long-term Debt Outstanding			$ 3,969.3		3,980.1
Long-term Debt Due Within One Year			249.5		249.2
Long-term Debt			3,719.8		3,730.9
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			11.7	$ 115.9
Accounts Receivable and Accrued Unbilled Revenues
Accounts Receivable and Accrued Unbilled Revenues			139.2		136.2
Fees Paid to AEP Credit for Customer Accounts Receivable Sold
Fees Paid to AEP Credit for Customer Accounts Receivable Sold			1.7	1.4
Proceeds from Sale of Receivables
Proceeds from Sale of Receivables to AEP Credit			400.2	369.7
Financing Activities (Textuals) [Abstract]
Reacquired Pollution Controls Bonds Held by Trustees			104.0
Repayments of Long-term Debt			$ 11.7	$ 115.9
Maximum Percentage Debt to Capitalization			67.50%
Appalachian Power Co [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 285.6
Maximum Loans to Money Pool			23.7
Average Borrowings from Money Pool			223.6
Average Loans to Money Pool			23.5
Net Loans (Borrowings) to/from Utility Money Pool			(222.4)
Authorized Short Term Borrowing Limit			$ 600.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.00%	1.04%
Average Interest Rate For Funds Loaned			2.00%	1.03%
Appalachian Power Co [Member] | Securitization Bonds [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 11.7
Debt Instrument, Interest Rate, Stated Percentage			2.008%
Due Date			2023
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 11.7
Due Date			2023
Indiana Michigan Power Co [Member]
Long-term Debt
Total Long-term Debt Outstanding			$ 2,717.2		2,745.1
Long-term Debt Due Within One Year			941.5		474.7
Long-term Debt			1,775.7		2,270.4
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			29.4	$ 109.5
Accounts Receivable and Accrued Unbilled Revenues
Accounts Receivable and Accrued Unbilled Revenues			147.8		136.5
Fees Paid to AEP Credit for Customer Accounts Receivable Sold
Fees Paid to AEP Credit for Customer Accounts Receivable Sold			2.1	1.5
Proceeds from Sale of Receivables
Proceeds from Sale of Receivables to AEP Credit			459.1	418.2
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 29.4	$ 109.5
Maximum Percentage Debt to Capitalization			67.50%
Indiana Michigan Power Co [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 314.1
Maximum Loans to Money Pool			12.5
Average Borrowings from Money Pool			240.6
Average Loans to Money Pool			12.5
Net Loans (Borrowings) to/from Utility Money Pool			(301.6)
Authorized Short Term Borrowing Limit			$ 500.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.02%	1.04%
Average Interest Rate For Funds Loaned			2.00%	1.03%
Indiana Michigan Power Co [Member] | Notes Payable [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 0.8
Interest Rate (Variable)			Variable
Due Date			2019
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 0.8
Due Date			2019
Indiana Michigan Power Co [Member] | Notes Payable [Member] | Subsequent Event [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments		$ 2.0
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt		$ 2.0
Indiana Michigan Power Co [Member] | Notes Payable Two [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 7.9
Interest Rate (Variable)			Variable
Due Date			2019
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 7.9
Due Date			2019
Indiana Michigan Power Co [Member] | Notes Payable Three [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 4.8
Interest Rate (Variable)			Variable
Due Date			2020
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 4.8
Due Date			2020
Indiana Michigan Power Co [Member] | Notes Payable Four [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 8.5
Interest Rate (Variable)			Variable
Due Date			2021
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 8.5
Due Date			2021
Indiana Michigan Power Co [Member] | Notes Payable Five [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 7.0
Interest Rate (Variable)			Variable
Due Date			2022
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 7.0
Due Date			2022
Indiana Michigan Power Co [Member] | Other Long Term Debt [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 0.4
Debt Instrument, Interest Rate, Stated Percentage			6.00%
Due Date			2025
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 0.4
Due Date			2025
Ohio Power Co [Member]
Long-term Debt
Total Long-term Debt Outstanding			$ 2,089.7		1,719.3
Long-term Debt Due Within One Year			397.5		397.0
Long-term Debt			1,692.2		1,322.3
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			22.9	$ 22.5
Accounts Receivable and Accrued Unbilled Revenues
Accounts Receivable and Accrued Unbilled Revenues			386.2		367.4
Fees Paid to AEP Credit for Customer Accounts Receivable Sold
Fees Paid to AEP Credit for Customer Accounts Receivable Sold			5.6	5.7
Proceeds from Sale of Receivables
Proceeds from Sale of Receivables to AEP Credit			680.0	632.3
Financing Activities (Textuals) [Abstract]
Reacquired Pollution Controls Bonds Held by Trustees			345.0
Repayments of Long-term Debt			22.9	$ 22.5
Ohio Power Co [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			229.1
Maximum Loans to Money Pool			216.4
Average Borrowings from Money Pool			104.9
Average Loans to Money Pool			179.5
Net Loans (Borrowings) to/from Utility Money Pool			200.4
Authorized Short Term Borrowing Limit			$ 400.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.00%	1.10%
Average Interest Rate For Funds Loaned			2.40%	0.98%
Ohio Power Co [Member] | Securitization Bonds [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 22.9
Debt Instrument, Interest Rate, Stated Percentage			2.049%
Due Date			2019
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 22.9
Due Date			2019
Ohio Power Co [Member] | Senior Unsecured Notes [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Issuances	[2]		$ 400.0
Debt Instrument, Interest Rate, Stated Percentage			4.15%
Due Date			2048
Financing Activities (Textuals) [Abstract]
Issuance of Long-term Debt	[2]		$ 400.0
Due Date			2048
Public Service Co Of Oklahoma [Member]
Long-term Debt
Total Long-term Debt Outstanding			$ 1,286.7		1,286.5
Long-term Debt Due Within One Year			0.5		0.5
Long-term Debt			1,286.2		1,286.0
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			0.1	$ 0.1
Accounts Receivable and Accrued Unbilled Revenues
Accounts Receivable and Accrued Unbilled Revenues			109.2		115.1
Fees Paid to AEP Credit for Customer Accounts Receivable Sold
Fees Paid to AEP Credit for Customer Accounts Receivable Sold			1.8	1.5
Proceeds from Sale of Receivables
Proceeds from Sale of Receivables to AEP Credit			332.6	286.8
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 0.1	$ 0.1
Maximum Percentage Debt to Capitalization			67.50%
Public Service Co Of Oklahoma [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 179.1
Maximum Loans to Money Pool			0.0
Average Borrowings from Money Pool			143.3
Average Loans to Money Pool			0.0
Net Loans (Borrowings) to/from Utility Money Pool			(179.1)
Authorized Short Term Borrowing Limit			$ 300.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.01%	1.06%
Average Interest Rate For Funds Loaned			0.00%	0.00%
Public Service Co Of Oklahoma [Member] | Other Long Term Debt [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 0.1
Debt Instrument, Interest Rate, Stated Percentage			3.00%
Due Date			2027
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 0.1
Due Date			2027
Southwestern Electric Power Co [Member]
Long-term Debt
Total Long-term Debt Outstanding			$ 2,503.7		2,441.9
Long-term Debt Due Within One Year			457.2		3.7
Long-term Debt			2,046.5		2,438.2
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			383.4	$ 251.7
Short-term Debt:
Notes Payable			22.6		22.0
Accounts Receivable and Accrued Unbilled Revenues
Accounts Receivable and Accrued Unbilled Revenues			130.6		$ 138.2
Fees Paid to AEP Credit for Customer Accounts Receivable Sold
Fees Paid to AEP Credit for Customer Accounts Receivable Sold			1.9	1.6
Proceeds from Sale of Receivables
Proceeds from Sale of Receivables to AEP Credit			397.6	341.2
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 383.4	$ 251.7
Maximum Percentage Debt to Capitalization			67.50%
Southwestern Electric Power Co [Member] | Utility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 169.1
Maximum Loans to Money Pool			296.5
Average Borrowings from Money Pool			143.7
Average Loans to Money Pool			273.2
Net Loans (Borrowings) to/from Utility Money Pool			(148.6)
Authorized Short Term Borrowing Limit			$ 350.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate			2.42%	1.27%
Minimum Interest Rate			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			2.10%	1.06%
Average Interest Rate For Funds Loaned			1.88%	0.98%
Southwestern Electric Power Co [Member] | Nonutility [Member]
Money Pool Participants Money Pool Activity And Authorized Borrowing Limits [Abstract]
Maximum Borrowings from Money Pool			$ 0.0
Maximum Loans to Money Pool			2.0
Average Borrowings from Money Pool			0.0
Average Loans to Money Pool			2.0
Net Loans (Borrowings) to/from Utility Money Pool			$ 2.0
Maximum and Minimum Interest Rates [Abstract]
Maximum Interest Rate for Funds Borrowed			0.00%	0.00%
Minimum Interest Rate For Funds Borrowed			0.00%	0.00%
Maximum Interest Rate For Funds Loaned			2.42%	1.27%
Minimum Interest Rate for Funds Loaned			1.83%	0.92%
Average Interest Rates for Funds Borrowed From and Loaned to Money Pool [Abstract]
Average Interest Rate For Funds Borrowed			0.00%	0.00%
Average Interest Rate For Funds Loaned			2.00%	1.03%
Southwestern Electric Power Co [Member] | Notes Payable [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 1.6
Debt Instrument, Interest Rate, Stated Percentage			4.58%
Due Date			2032
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 1.6
Due Date			2032
Southwestern Electric Power Co [Member] | Other Long Term Debt [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 0.1
Debt Instrument, Interest Rate, Stated Percentage			3.50%
Due Date			2023
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 0.1
Due Date			2023
Southwestern Electric Power Co [Member] | Pollution Control Bonds [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 81.7
Debt Instrument, Interest Rate, Stated Percentage			4.95%
Due Date			2018
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 81.7
Due Date			2018
Southwestern Electric Power Co [Member] | Senior Unsecured Notes [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Issuances	[2]		$ 450.0
Debt Instrument, Interest Rate, Stated Percentage			3.85%
Due Date			2048
Financing Activities (Textuals) [Abstract]
Issuance of Long-term Debt	[2]		$ 450.0
Due Date			2048
Southwestern Electric Power Co [Member] | Senior Unsecured Notes Two [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Retirements and Principal Payments			$ 300.0
Debt Instrument, Interest Rate, Stated Percentage			5.875%
Due Date			2018
Financing Activities (Textuals) [Abstract]
Repayments of Long-term Debt			$ 300.0
Due Date			2018
Transource Energy [Member] | Other Long Term Debt [Member]
Long-term Debt and Other Securities Issued, Retired and Principal Payments Made
Issuances	[2]		$ 3.4
Interest Rate (Variable)			Variable
Due Date			2020
Financing Activities (Textuals) [Abstract]
Issuance of Long-term Debt	[2]		$ 3.4
Due Date			2020
Commercial Paper [Member]
Short-term Debt:
Weighted Average Interest Rate	[4]		2.41%		1.85%
Loans Payable [Member]
Short-term Debt:
Weighted Average Interest Rate	[4]		3.20%		2.92%
Loans Payable [Member] | Southwestern Electric Power Co [Member]
Short-term Debt:
Weighted Average Interest Rate	[4]		3.20%		2.92%

[1] Pursuant to the Nuclear Waste Policy Act of 1982, I&M, a nuclear licensee, has an obligation to the United States Department of Energy for spent nuclear fuel disposal. The obligation includes a one-time fee for nuclear fuel consumed prior to April 7, 1983. Trust fund assets related to this obligation were $313 million and $312 million as of March 31, 2018 and December 31, 2017, respectively, and are included in Spent Nuclear Fuel and Decommissioning Trusts on the balance sheets.

[2] Amounts indicated on the statements of cash flows are net of issuance costs and premium or discount and will not tie to the issuance amounts.

[3] Amount of securitized debt for receivables as accounted for under the “Transfers and Servicing” accounting guidance.

[4] Weighted average rate.

[5] (a)Amount represents the combined authorized short-term borrowing limit the State Transcos have from FERC or state regulatory commissions.

[6] (a)Amount represents the combined authorized short-term borrowing limit the State Transcos have from FERC or state regulatory commissions.