Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Lease Rental Costs
Operating Lease, Cost	$ 279.6		$ 286.0		$ 245.0
Finance Lease Right-of-Use Asset Amortization	61.9		70.8		62.4
Interest Expense on Finance Leases	15.4		16.4		16.4
Total Lease Rental Costs	$ 356.9	[1]	$ 373.2	[1]	323.8
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	5 years 3 months 18 days		5 years 2 months 23 days
Weighted Average Remaining Lease Term, Finance Leases	5 years 5 months 4 days		5 years 10 months 6 days
Weighted Average Discount Rate, Operating Leases	3.44%		3.60%
Weighted Average Discount Rate, Finance Leases	5.68%		5.98%
Operating Cash Flows Used for Operating Leases	$ 280.3		$ 284.7
Operating Cash Flows Used for Finance Leases	15.4		16.4
Financing Cash Flows Used for Finance Leases	61.7		70.7		65.1
Non-cash Acquisitions Under Operating Leases	161.7		125.0
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	23,133.9		22,762.4
Other Property, Plant and Equipment	5,294.6		4,811.5
Total Property, Plant and Equipment	84,313.0		79,145.7
Accumulated Amortization	20,411.4		19,007.6
Net Property, Plant and Equipment Under Finance Leases	284.2		303.1
Other Liabilities, Noncurrent	728.0		719.8
Finance Lease Liability Due Within One Year	1,199.3		1,373.8
Total Obligations Under Finance Leases	289.1		306.8
Operating Lease Asset and Related Obligations
Operating Lease Assets	866.4		957.4
Operating Lease Noncurrent Liability	638.4		734.6
Operating Lease Liability Due Within One Year	241.3		234.1
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	879.7		968.7
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	72.2		72.7
Year 2	64.0		64.9
Year 3	56.2		56.4
Year 4	63.5		49.6
Year 5	32.7		57.4
Finance Leases, Later Years	48.9		64.4
Finance Leases, Total Future Minimum Lease Payments	337.5		365.4
Imputed Interest on Finance Leases	48.4		58.6
Total Obligations Under Finance Leases	289.1		306.8
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	270.8		269.9
Year 2	263.3		253.6
Year 3	94.2		245.6
Year 4	81.6		74.8
Year 5	68.0		62.0
Operating Leases, Later Years	193.0		169.7
Operating Leases, Total Future Minimum Lease Payments	970.9		1,075.6
Imputed Interest on Operating Leases	91.2		106.9
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	879.7		968.7
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	50.3
Rockport Lease [Member]
Future Minimum Rentals, Sale Leaseback Transactions
2021	147.8
2022	147.6
Total Future Minimum Lease Payments	295.4
Leases (Textuals)
Sale and Leaseback Transaction, Gain (Loss), Net	$ 37.0
Lease Term	33 years
Boat and Barge Leases [Member]
Leases (Textuals)
Maximum Potential Lease Payments, AEPRO Barge and Boat Leases	$ 48.0
Guarantor Obligations, Current Carrying Value	3.0
Guarantee Obligations Current Carrying Value Other Liabilities Current	1.0
Guarantee Obligations Current Carrying Value Other Liabilities Noncurrent	2.0
Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	138.2		131.6
Other Property, Plant and Equipment	322.8		323.0
Total Property, Plant and Equipment	461.0		454.6
Accumulated Amortization	176.8		151.5
Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	231.0		249.2
Finance Lease Liability Due Within One Year	58.1		57.6
Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	866.4		957.4
AEP Texas Inc. [Member]
Lease Rental Costs
Operating Lease, Cost	17.4		16.5		13.6
Finance Lease Right-of-Use Asset Amortization	6.3		5.1		4.8
Interest Expense on Finance Leases	1.5		1.4		1.2
Total Lease Rental Costs	$ 25.2	[1]	$ 23.0	[1]	19.6
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	6 years 6 months 3 days		6 years 11 months 4 days
Weighted Average Remaining Lease Term, Finance Leases	6 years 25 days		6 years 8 months 8 days
Weighted Average Discount Rate, Operating Leases	3.60%		3.77%
Weighted Average Discount Rate, Finance Leases	4.39%		4.62%
Operating Cash Flows Used for Operating Leases	$ 17.1		$ 15.3
Operating Cash Flows Used for Finance Leases	1.5		1.4
Financing Cash Flows Used for Finance Leases	6.3		5.1		4.7
Non-cash Acquisitions Under Operating Leases	15.8		13.8
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	0.0		351.7
Other Property, Plant and Equipment	868.4		805.9
Total Property, Plant and Equipment	11,342.9		10,603.2
Accumulated Amortization	1,529.3		1,758.1
Net Property, Plant and Equipment Under Finance Leases	33.1		34.1
Other Liabilities, Noncurrent	57.2		81.1
Finance Lease Liability Due Within One Year	88.5		123.3
Total Obligations Under Finance Leases	33.1		34.1
Operating Lease Asset and Related Obligations
Operating Lease Noncurrent Liability	71.0		71.1
Operating Lease Liability Due Within One Year	14.5		12.0
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	85.5		83.1
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	7.6		7.3
Year 2	6.9		6.7
Year 3	6.2		6.0
Year 4	5.4		5.4
Year 5	4.0		4.6
Finance Leases, Later Years	7.8		9.8
Finance Leases, Total Future Minimum Lease Payments	37.9		39.8
Imputed Interest on Finance Leases	4.8		5.7
Total Obligations Under Finance Leases	33.1		34.1
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	17.5		16.0
Year 2	16.4		15.3
Year 3	14.8		14.2
Year 4	13.3		13.0
Year 5	10.9		11.4
Operating Leases, Later Years	23.9		26.0
Operating Leases, Total Future Minimum Lease Payments	96.8		95.9
Imputed Interest on Operating Leases	11.3		12.8
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	85.5		83.1
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	11.7
AEP Texas Inc. [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	0.0		0.0
Other Property, Plant and Equipment	49.7		45.9
Total Property, Plant and Equipment	49.7		45.9
Accumulated Amortization	16.6		11.8
AEP Texas Inc. [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	26.8		28.2
Finance Lease Liability Due Within One Year	6.3		5.9
AEP Texas Inc. [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	84.1		81.8
AEP Transmission Co [Member]
Lease Rental Costs
Operating Lease, Cost	2.6		2.5		2.7
Finance Lease Right-of-Use Asset Amortization	0.0		0.1		0.1
Interest Expense on Finance Leases	0.0		0.0		0.0
Total Lease Rental Costs	$ 2.6	[1]	$ 2.6	[1]	2.8
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	2 years 3 days		2 years 3 months
Weighted Average Remaining Lease Term, Finance Leases	0 years		3 months
Weighted Average Discount Rate, Operating Leases	1.51%		3.14%
Weighted Average Discount Rate, Finance Leases	0.00%		9.33%
Operating Cash Flows Used for Operating Leases	$ 2.6		$ 2.4
Operating Cash Flows Used for Finance Leases	0.0		0.0
Financing Cash Flows Used for Finance Leases	0.0		0.0
Non-cash Acquisitions Under Operating Leases	1.8		0.6
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Property, Plant and Equipment	329.5		269.6
Total Property, Plant and Equipment	11,345.6		9,893.2
Accumulated Amortization	572.8		402.3
Net Property, Plant and Equipment Under Finance Leases	0.0		0.0
Other Liabilities, Noncurrent	8.0		0.3
Finance Lease Liability Due Within One Year	9.9		14.6
Total Obligations Under Finance Leases	0.0		0.0
Operating Lease Asset and Related Obligations
Operating Lease Noncurrent Liability	0.4		1.9
Operating Lease Liability Due Within One Year	1.2		2.1
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	1.6		4.0
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	0.0		0.0
Year 2	0.0		0.0
Year 3	0.0		0.0
Year 4	0.0		0.0
Year 5	0.0		0.0
Finance Leases, Later Years	0.0		0.0
Finance Leases, Total Future Minimum Lease Payments	0.0		0.0
Imputed Interest on Finance Leases	0.0		0.0
Total Obligations Under Finance Leases	0.0		0.0
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	1.2		2.2
Year 2	0.2		1.2
Year 3	0.1		0.6
Year 4	0.1		0.1
Year 5	0.0		0.0
Operating Leases, Later Years	0.0		0.0
Operating Leases, Total Future Minimum Lease Payments	1.6		4.1
Imputed Interest on Operating Leases	0.0		0.1
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	1.6		4.0
AEP Transmission Co [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	0.0		0.0
Other Property, Plant and Equipment	0.0		0.2
Total Property, Plant and Equipment	0.0		0.2
Accumulated Amortization	0.0		0.2
AEP Transmission Co [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	0.0		0.0
Finance Lease Liability Due Within One Year	0.0		0.0
AEP Transmission Co [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	1.6		3.8
Appalachian Power Co [Member]
Lease Rental Costs
Operating Lease, Cost	19.1		19.5		18.2
Finance Lease Right-of-Use Asset Amortization	7.4		6.7		7.0
Interest Expense on Finance Leases	2.7		2.9		3.0
Total Lease Rental Costs	$ 29.2	[1]	$ 29.1	[1]	28.2
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	6 years 3 months 7 days		6 years 3 months 10 days
Weighted Average Remaining Lease Term, Finance Leases	5 years 9 months		6 years 1 month 13 days
Weighted Average Discount Rate, Operating Leases	3.48%		3.64%
Weighted Average Discount Rate, Finance Leases	7.33%		8.08%
Operating Cash Flows Used for Operating Leases	$ 19.2		$ 19.0
Operating Cash Flows Used for Finance Leases	2.7		2.9
Financing Cash Flows Used for Finance Leases	7.4		6.7		6.9
Non-cash Acquisitions Under Operating Leases	16.2		10.2
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	6,633.7		6,563.7
Other Property, Plant and Equipment	627.2		571.3
Total Property, Plant and Equipment	16,110.3		15,514.2
Accumulated Amortization	4,716.2		4,432.3
Net Property, Plant and Equipment Under Finance Leases	41.7		41.8
Other Liabilities, Noncurrent	49.6		55.2
Finance Lease Liability Due Within One Year	164.5		170.9
Total Obligations Under Finance Leases	41.7		41.8
Operating Lease Asset and Related Obligations
Operating Lease Assets	78.8		78.5
Operating Lease Noncurrent Liability	64.4		64.0
Operating Lease Liability Due Within One Year	14.9		15.2
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	79.3		79.2
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	9.9		9.6
Year 2	9.4		8.9
Year 3	8.7		8.2
Year 4	8.1		7.7
Year 5	7.0		7.1
Finance Leases, Later Years	6.4		9.8
Finance Leases, Total Future Minimum Lease Payments	49.5		51.3
Imputed Interest on Finance Leases	7.8		9.5
Total Obligations Under Finance Leases	41.7		41.8
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	17.7		18.3
Year 2	17.0		15.7
Year 3	14.2		14.7
Year 4	11.3		11.9
Year 5	8.5		9.0
Operating Leases, Later Years	20.0		20.0
Operating Leases, Total Future Minimum Lease Payments	88.7		89.6
Imputed Interest on Operating Leases	9.4		10.4
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	79.3		79.2
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	6.6
Appalachian Power Co [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	42.8		39.9
Other Property, Plant and Equipment	20.3		18.9
Total Property, Plant and Equipment	63.1		58.8
Accumulated Amortization	21.4		17.0
Appalachian Power Co [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	34.4		35.0
Finance Lease Liability Due Within One Year	7.3		6.8
Appalachian Power Co [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	78.8		78.5
Indiana Michigan Power Co [Member]
Lease Rental Costs
Operating Lease, Cost	101.5		93.1		89.2
Finance Lease Right-of-Use Asset Amortization	6.5		5.7		6.6
Interest Expense on Finance Leases	3.1		2.9		3.3
Total Lease Rental Costs	$ 111.1	[1]	$ 101.7	[1]	99.1
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	3 years 6 months		3 years 10 months 28 days
Weighted Average Remaining Lease Term, Finance Leases	5 years 9 months 14 days		6 years 6 months 18 days
Weighted Average Discount Rate, Operating Leases	3.42%		3.45%
Weighted Average Discount Rate, Finance Leases	8.29%		8.47%
Operating Cash Flows Used for Operating Leases	$ 102.2		$ 94.3
Operating Cash Flows Used for Finance Leases	3.1		3.1
Financing Cash Flows Used for Finance Leases	6.5		5.7		8.8
Non-cash Acquisitions Under Operating Leases	18.1		18.7
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	5,264.7		5,099.7
Other Property, Plant and Equipment	686.7		632.6
Total Property, Plant and Equipment	10,604.8		10,194.0
Accumulated Amortization	3,552.5		3,294.3
Net Property, Plant and Equipment Under Finance Leases	41.7		45.1
Other Liabilities, Noncurrent	69.2		67.8
Finance Lease Liability Due Within One Year	112.0		110.1
Total Obligations Under Finance Leases	41.7		45.1
Operating Lease Asset and Related Obligations
Operating Lease Assets	218.1		294.9
Operating Lease Noncurrent Liability	135.9		211.6
Operating Lease Liability Due Within One Year	85.6		87.3
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	221.5		298.9
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	9.3		9.4
Year 2	8.6		8.7
Year 3	7.9		8.0
Year 4	11.1		7.5
Year 5	5.5		10.8
Finance Leases, Later Years	12.2		16.4
Finance Leases, Total Future Minimum Lease Payments	54.6		60.8
Imputed Interest on Finance Leases	12.9		15.7
Total Obligations Under Finance Leases	41.7		45.1
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	92.5		97.0
Year 2	92.5		92.9
Year 3	11.4		92.8
Year 4	10.0		10.1
Year 5	8.9		8.6
Operating Leases, Later Years	21.8		21.0
Operating Leases, Total Future Minimum Lease Payments	237.1		322.4
Imputed Interest on Operating Leases	15.6		23.5
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	221.5		298.9
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	4.4
Indiana Michigan Power Co [Member] | Rockport Lease [Member]
Future Minimum Rentals, Sale Leaseback Transactions
2021	73.9
2022	73.8
Total Future Minimum Lease Payments	147.7
Leases (Textuals)
Sale and Leaseback Transaction, Gain (Loss), Net	$ 15.0
Lease Term	33 years
Indiana Michigan Power Co [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	$ 28.8		28.8
Other Property, Plant and Equipment	40.2		39.3
Total Property, Plant and Equipment	69.0		68.1
Accumulated Amortization	27.3		23.0
Indiana Michigan Power Co [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	35.3		38.8
Finance Lease Liability Due Within One Year	6.4		6.3
Indiana Michigan Power Co [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	218.1		294.9
Ohio Power Co [Member]
Lease Rental Costs
Operating Lease, Cost	17.1		18.0		10.7
Finance Lease Right-of-Use Asset Amortization	4.7		3.5		3.9
Interest Expense on Finance Leases	0.9		0.7		0.5
Total Lease Rental Costs	$ 22.7	[1]	$ 22.2	[1]	15.1
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	7 years 5 months 8 days		7 years 11 months 8 days
Weighted Average Remaining Lease Term, Finance Leases	5 years 10 months 24 days		6 years 5 months 26 days
Weighted Average Discount Rate, Operating Leases	3.60%		3.76%
Weighted Average Discount Rate, Finance Leases	4.25%		4.54%
Operating Cash Flows Used for Operating Leases	$ 16.9		$ 18.0
Operating Cash Flows Used for Finance Leases	0.9		0.7
Financing Cash Flows Used for Finance Leases	4.7		3.5		3.8
Non-cash Acquisitions Under Operating Leases	18.1		35.4
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Property, Plant and Equipment	899.6		765.8
Total Property, Plant and Equipment	9,802.1		9,170.0
Accumulated Amortization	2,350.0		2,263.0
Net Property, Plant and Equipment Under Finance Leases	21.6		20.1
Other Liabilities, Noncurrent	40.0		42.7
Finance Lease Liability Due Within One Year	139.6		151.2
Total Obligations Under Finance Leases	21.6		20.1
Operating Lease Asset and Related Obligations
Operating Lease Noncurrent Liability	79.5		76.0
Operating Lease Liability Due Within One Year	13.1		12.5
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	92.6		88.5
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	5.5		4.7
Year 2	4.6		4.3
Year 3	3.9		3.4
Year 4	3.3		2.8
Year 5	2.2		2.4
Finance Leases, Later Years	4.9		5.7
Finance Leases, Total Future Minimum Lease Payments	24.4		23.3
Imputed Interest on Finance Leases	2.8		3.2
Total Obligations Under Finance Leases	21.6		20.1
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	16.6		16.2
Year 2	16.0		14.2
Year 3	14.9		13.5
Year 4	13.2		12.3
Year 5	11.5		10.7
Operating Leases, Later Years	34.0		36.5
Operating Leases, Total Future Minimum Lease Payments	106.2		103.4
Imputed Interest on Operating Leases	13.6		14.9
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	92.6		88.5
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	8.1
Ohio Power Co [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	0.0		0.0
Other Property, Plant and Equipment	31.4		27.3
Total Property, Plant and Equipment	31.4		27.3
Accumulated Amortization	9.8		7.2
Ohio Power Co [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	16.9		16.2
Finance Lease Liability Due Within One Year	4.7		3.9
Ohio Power Co [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	92.0		88.0
Public Service Co Of Oklahoma [Member]
Lease Rental Costs
Operating Lease, Cost	7.8		6.8		5.7
Finance Lease Right-of-Use Asset Amortization	3.5		3.1		3.2
Interest Expense on Finance Leases	0.7		0.6		0.4
Total Lease Rental Costs	$ 12.0	[1]	$ 10.5	[1]	9.3
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	7 years 10 days		7 years 25 days
Weighted Average Remaining Lease Term, Finance Leases	6 years 1 month 28 days		6 years 2 months 23 days
Weighted Average Discount Rate, Operating Leases	3.39%		3.64%
Weighted Average Discount Rate, Finance Leases	4.35%		4.62%
Operating Cash Flows Used for Operating Leases	$ 7.7		$ 6.7
Operating Cash Flows Used for Finance Leases	0.7		0.6
Financing Cash Flows Used for Finance Leases	3.5		3.1		3.3
Non-cash Acquisitions Under Operating Leases	12.3		8.2
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	1,480.7		1,574.6
Other Property, Plant and Equipment	393.3		342.1
Total Property, Plant and Equipment	5,925.6		5,683.4
Accumulated Amortization	1,605.6		1,580.1
Net Property, Plant and Equipment Under Finance Leases	15.0		15.1
Other Liabilities, Noncurrent	20.6		18.4
Finance Lease Liability Due Within One Year	84.2		87.5
Total Obligations Under Finance Leases	15.0		15.1
Operating Lease Asset and Related Obligations
Operating Lease Assets	42.6		36.8
Operating Lease Noncurrent Liability	36.2		31.0
Operating Lease Liability Due Within One Year	6.5		5.8
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	42.7		36.8
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	3.6		3.8
Year 2	3.1		3.2
Year 3	2.7		2.6
Year 4	2.3		2.3
Year 5	1.6		1.8
Finance Leases, Later Years	3.8		3.8
Finance Leases, Total Future Minimum Lease Payments	17.1		17.5
Imputed Interest on Finance Leases	2.1		2.4
Total Obligations Under Finance Leases	15.0		15.1
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	7.9		7.3
Year 2	7.6		6.4
Year 3	7.3		6.0
Year 4	6.5		5.6
Year 5	5.4		4.8
Operating Leases, Later Years	13.3		12.0
Operating Leases, Total Future Minimum Lease Payments	48.0		42.1
Imputed Interest on Operating Leases	5.3		5.3
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	42.7		36.8
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	4.8
Public Service Co Of Oklahoma [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	0.7		0.6
Other Property, Plant and Equipment	23.0		21.6
Total Property, Plant and Equipment	23.7		22.2
Accumulated Amortization	8.7		7.1
Public Service Co Of Oklahoma [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	11.9		11.9
Finance Lease Liability Due Within One Year	3.1		3.2
Public Service Co Of Oklahoma [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	42.6		36.8
Southwestern Electric Power Co [Member]
Lease Rental Costs
Operating Lease, Cost	9.4		8.0		6.5
Finance Lease Right-of-Use Asset Amortization	10.9		11.0		11.2
Interest Expense on Finance Leases	2.2		2.9		3.2
Total Lease Rental Costs	$ 22.5	[1]	$ 21.9	[1]	20.9
Supplemental Information Related to Leases
Weighted-Average Remaining Lease Term, Operating Leases	7 years 6 months 14 days		6 years 7 months 20 days
Weighted Average Remaining Lease Term, Finance Leases	4 years 11 months 12 days		5 years 1 month 28 days
Weighted Average Discount Rate, Operating Leases	3.45%		3.76%
Weighted Average Discount Rate, Finance Leases	4.77%		5.01%
Operating Cash Flows Used for Operating Leases	$ 9.4		$ 7.9
Operating Cash Flows Used for Finance Leases	2.2		3.0
Financing Cash Flows Used for Finance Leases	10.9		11.0		$ 11.5
Non-cash Acquisitions Under Operating Leases	18.4		11.4
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	4,681.4		4,691.4
Other Property, Plant and Equipment	788.8		733.4
Total Property, Plant and Equipment	10,246.7		9,968.9
Accumulated Amortization	3,158.5		2,873.7
Net Property, Plant and Equipment Under Finance Leases	53.6		57.3
Other Liabilities, Noncurrent	94.2		86.2
Finance Lease Liability Due Within One Year	173.4		133.9
Total Obligations Under Finance Leases	55.3		57.6
Operating Lease Asset and Related Obligations
Operating Lease Noncurrent Liability	44.1		34.7
Operating Lease Liability Due Within One Year	7.9		6.5
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	52.0		41.2
Finance Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	13.1		12.9
Year 2	11.8		11.9
Year 3	10.9		10.6
Year 4	15.3		9.8
Year 5	5.7		14.2
Finance Leases, Later Years	5.8		6.8
Finance Leases, Total Future Minimum Lease Payments	62.6		66.2
Imputed Interest on Finance Leases	7.3		8.6
Total Obligations Under Finance Leases	55.3		57.6
Operating Lease Liabilities Rolling Future Minimum Lease Payments
Year 1	10.1		8.6
Year 2	9.6		8.2
Year 3	8.4		7.6
Year 4	6.9		6.4
Year 5	5.8		5.0
Operating Leases, Later Years	17.4		11.8
Operating Leases, Total Future Minimum Lease Payments	58.2		47.6
Imputed Interest on Operating Leases	6.2		6.4
Estimated Present Value of Future Minimum Lease Payments on Operating Leases	52.0		41.2
Maximum Potential Loss
Max Potential Loss on Master Lease Agreements	5.4
Southwestern Electric Power Co [Member] | Finance Lease Assets [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Generation	37.7		34.1
Other Property, Plant and Equipment	52.4		51.6
Total Property, Plant and Equipment	90.1		85.7
Accumulated Amortization	36.5		28.4
Southwestern Electric Power Co [Member] | Finance Lease Liabilities [Member]
Property, Plant and Equipment and Other Related Obligations Under Finance Leases
Other Liabilities, Noncurrent	44.6		47.1
Finance Lease Liability Due Within One Year	10.7		10.5
Southwestern Electric Power Co [Member] | Operating Lease Assets [Member]
Operating Lease Asset and Related Obligations
Operating Lease Assets	$ 48.5		$ 40.5

[1] Excludes variable and short-term lease costs, which were immaterial for the twelve months ended December 31, 2020 and December 31, 2019.