Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		$ (120.4)	$ (67.8)
Change in Fair Value Recognized in AOCI		(38.8)	12.8
Interest Rate
Interest Expense		255.8	234.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		10.7	(14.6)
Income Tax (Expense) Benefit		(44.5)	(102.0)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		8.5	(11.5)
Net Current Period Other Comprehensive Income (Loss)		(30.3)	1.3
ASU 2018-02 Adoption			(3.0)
ASU 2016-01 Adoption			0.0
Ending Balance in AOCI		(150.7)	(95.4)
Securities Available for Sale [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI			11.9
Change in Fair Value Recognized in AOCI			0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit			0.0
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit			0.0
Net Current Period Other Comprehensive Income (Loss)			0.0
ASU 2018-02 Adoption			0.0
ASU 2016-01 Adoption			(11.9)
Ending Balance in AOCI			0.0
Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(84.8)	(38.3)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(1.8)	(1.8)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(1.4)	(1.4)
Net Current Period Other Comprehensive Income (Loss)		(1.4)	(1.4)
ASU 2018-02 Adoption			(8.2)
ASU 2016-01 Adoption			0.0
Ending Balance in AOCI		(86.2)	(47.9)
Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		(30.3)	1.3
ASU 2018-02 Adoption			(17.0)
ASU 2016-01 Adoption			(11.9)
Commodity [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(23.0)	(28.4)
Change in Fair Value Recognized in AOCI		(38.8)	12.8
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		12.3	(13.1)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		9.7	(10.3)
Net Current Period Other Comprehensive Income (Loss)		(29.1)	2.5
ASU 2018-02 Adoption			(6.1)
ASU 2016-01 Adoption			0.0
Ending Balance in AOCI		(52.1)	(32.0)
Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(12.6)	(13.0)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.2	0.3
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.2	0.2
Net Current Period Other Comprehensive Income (Loss)		0.2	0.2
ASU 2018-02 Adoption			(2.7)
ASU 2016-01 Adoption			0.0
Ending Balance in AOCI		(12.4)	(15.5)
Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		861.8	990.3
Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[1]	0.2	0.3
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(4.8)	(5.0)
Amortization of Actuarial (Gains) Losses		3.0	3.2
Income Tax (Expense) Benefit		2.2	(3.1)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Securities Available for Sale [Member]
Interest Rate
Interest Expense	[1]		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)			0.0
Amortization of Actuarial (Gains) Losses			0.0
Income Tax (Expense) Benefit			0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[1]	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(4.8)	(5.0)
Amortization of Actuarial (Gains) Losses		3.0	3.2
Income Tax (Expense) Benefit		(0.4)	(0.4)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains) Losses		0.0	0.0
Income Tax (Expense) Benefit		2.6	(2.8)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	0.2	0.3
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains) Losses		0.0	0.0
Income Tax (Expense) Benefit		0.0	0.1
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale	[1]	12.3	(13.1)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Securities Available for Sale [Member]
Commodity
Purchased Electricity for Resale	[1]		0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Pension and OPEB [Member]
Commodity
Purchased Electricity for Resale	[1]	0.0	0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[1]	12.3	(13.1)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[1]	0.0	0.0
AEP Texas Inc. [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(15.1)	(12.6)
Change in Fair Value Recognized in AOCI		0.0	0.0
Interest Rate
Interest Expense		37.4	35.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.4	0.4
Income Tax (Expense) Benefit		(4.0)	(9.1)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.3	0.3
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3
ASU 2018-02 Adoption			(0.9)
Ending Balance in AOCI		(14.8)	(15.0)
AEP Texas Inc. [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(10.7)	(8.1)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.0	0.1
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.0	0.1
Net Current Period Other Comprehensive Income (Loss)		0.0	0.1
ASU 2018-02 Adoption			(1.8)
Ending Balance in AOCI		(10.7)	(9.8)
AEP Texas Inc. [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3
ASU 2018-02 Adoption			(2.7)
AEP Texas Inc. [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(4.4)	(4.5)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.4	0.3
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.3	0.2
Net Current Period Other Comprehensive Income (Loss)		0.3	0.2
ASU 2018-02 Adoption			(0.9)
Ending Balance in AOCI		(4.1)	(5.2)
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[1]	0.4	0.3
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Actuarial (Gains) Losses			0.1
Income Tax (Expense) Benefit		0.1	0.1
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[1]	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Actuarial (Gains) Losses			0.1
Income Tax (Expense) Benefit		0.0	0.0
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	0.4	0.3
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Actuarial (Gains) Losses			0.0
Income Tax (Expense) Benefit		0.1	0.1
Appalachian Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(5.0)	1.3
Change in Fair Value Recognized in AOCI		0.0	(0.7)
Interest Rate
Interest Expense		49.3	47.4
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(1.1)	(0.4)
Income Tax (Expense) Benefit		24.1	(28.0)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(0.8)	(0.3)
Net Current Period Other Comprehensive Income (Loss)		(0.8)	(1.0)
ASU 2018-02 Adoption			0.4
Ending Balance in AOCI		(5.8)	0.6
Appalachian Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(6.8)	(0.9)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(0.8)	(1.0)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(0.6)	(0.8)
Net Current Period Other Comprehensive Income (Loss)		(0.6)	(0.8)
ASU 2018-02 Adoption			(0.2)
Ending Balance in AOCI		(7.4)	(1.9)
Appalachian Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		(0.8)	(1.0)
ASU 2018-02 Adoption			0.3
Appalachian Power Co [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI			0.0
Change in Fair Value Recognized in AOCI			(0.7)
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit			0.9
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit			0.7
Net Current Period Other Comprehensive Income (Loss)			0.0
ASU 2018-02 Adoption			0.0
Ending Balance in AOCI			0.0
Appalachian Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.8	2.2
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(0.3)	(0.3)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(0.2)	(0.2)
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption			0.5
Ending Balance in AOCI		1.6	2.5
Appalachian Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		110.6	205.9
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[1]	(0.3)	(0.3)
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.3)	(1.3)
Amortization of Actuarial (Gains) Losses		0.5	0.3
Income Tax (Expense) Benefit		(0.3)	(0.1)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[1]	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.3)	(1.3)
Amortization of Actuarial (Gains) Losses		0.5	0.3
Income Tax (Expense) Benefit		(0.2)	(0.2)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)			0.0
Amortization of Actuarial (Gains) Losses			0.0
Income Tax (Expense) Benefit			0.2
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	(0.3)	(0.3)
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains) Losses		0.0	0.0
Income Tax (Expense) Benefit		(0.1)	(0.1)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale	[1]		0.9
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Pension and OPEB [Member]
Commodity
Purchased Electricity for Resale	[1]		0.0
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[1]		0.9
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[1]		0.0
Indiana Michigan Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(13.8)	(12.1)
Change in Fair Value Recognized in AOCI		0.0	0.0
Interest Rate
Interest Expense		28.9	29.7
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.5	0.5
Income Tax (Expense) Benefit		2.7	(12.4)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.4	0.4
Net Current Period Other Comprehensive Income (Loss)		0.4	0.4
ASU 2018-02 Adoption			(2.4)
Ending Balance in AOCI		(13.4)	(14.4)
Indiana Michigan Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(2.3)	(1.4)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.0	0.0
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.0	0.0
Net Current Period Other Comprehensive Income (Loss)		0.0	0.0
ASU 2018-02 Adoption			(0.3)
Ending Balance in AOCI		(2.3)	(1.7)
Indiana Michigan Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		0.4	0.4
ASU 2018-02 Adoption			(2.7)
Indiana Michigan Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(11.5)	(10.7)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.5	0.5
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.4	0.4
Net Current Period Other Comprehensive Income (Loss)		0.4	0.4
ASU 2018-02 Adoption			(2.4)
Ending Balance in AOCI		(11.1)	(12.7)
Indiana Michigan Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		69.6	55.6
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[1]	0.5	0.5
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)	(0.2)
Amortization of Actuarial (Gains) Losses		0.2	0.2
Income Tax (Expense) Benefit		0.1	0.1
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[1]	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)	(0.2)
Amortization of Actuarial (Gains) Losses		0.2	0.2
Income Tax (Expense) Benefit		0.0	0.0
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	0.5	0.5
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains) Losses		0.0	0.0
Income Tax (Expense) Benefit		0.1	0.1
Ohio Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.0
Interest Rate
Interest Expense		24.6	25.2
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		(19.8)	(20.5)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.3)
ASU 2018-02 Adoption			0.4
Ending Balance in AOCI		0.7
Ohio Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.3)
ASU 2018-02 Adoption			0.4
Ohio Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.0	1.9
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(0.4)	(0.4)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(0.3)	(0.3)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.3)
ASU 2018-02 Adoption			0.4
Ending Balance in AOCI		0.7	2.0
Ohio Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		174.2	205.5
Ohio Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	(0.4)	(0.4)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		(0.1)	(0.1)
Public Service Co Of Oklahoma [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.1
Interest Rate
Interest Expense		16.9	14.7
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		0.0	1.4
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption			0.5
Ending Balance in AOCI		1.9
Public Service Co Of Oklahoma [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption			0.5
Public Service Co Of Oklahoma [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.1	2.6
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(0.3)	(0.3)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(0.2)	(0.2)
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption			0.5
Ending Balance in AOCI		1.9	2.9
Public Service Co Of Oklahoma [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		122.9	122.4
Public Service Co Of Oklahoma [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	(0.3)	(0.3)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		(0.1)	(0.1)
Southwestern Electric Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(5.4)	(4.0)
Change in Fair Value Recognized in AOCI		0.0	0.0
Interest Rate
Interest Expense		29.7	32.2
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.1	0.1
Income Tax (Expense) Benefit		(0.7)	(2.9)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.1	0.1
Net Current Period Other Comprehensive Income (Loss)		0.1	0.1
ASU 2018-02 Adoption			(1.3)
Ending Balance in AOCI		(5.3)	(4.8)
Southwestern Electric Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(2.1)	2.0
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		(0.4)	(0.4)
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		(0.3)	(0.3)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.3)
ASU 2018-02 Adoption			0.4
Ending Balance in AOCI		(2.4)	2.1
Southwestern Electric Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		0.1	0.1
ASU 2018-02 Adoption			(0.9)
Southwestern Electric Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(3.3)	(6.0)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassifications from AOCI, before Income Tax (Expense) Benefit		0.5	0.5
Reclassifications from AOCI, Net of Income Tax (Expense) Benefit		0.4	0.4
Net Current Period Other Comprehensive Income (Loss)		0.4	0.4
ASU 2018-02 Adoption			(1.3)
Ending Balance in AOCI		(2.9)	(6.9)
Southwestern Electric Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		32.6	42.7
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[1]	0.5	0.5
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.5)	(0.5)
Amortization of Actuarial (Gains) Losses		0.1	0.1
Income Tax (Expense) Benefit		0.0	0.0
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[1]	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.5)	(0.5)
Amortization of Actuarial (Gains) Losses		0.1	0.1
Income Tax (Expense) Benefit		(0.1)	(0.1)
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[1]	0.5	0.5
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains) Losses		0.0	0.0
Income Tax (Expense) Benefit		$ 0.1	$ 0.1

[1] Amounts reclassified to the referenced line item on the statements of income.