Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans [Member]
Components of Net Periodic Benefit Cost
Service Cost	$ 23,000	$ 18,000	$ 70,000	$ 54,000
Interest Cost	51,000	55,000	154,000	166,000
Expected Return on Plan Assets	(69,000)	(65,000)	(206,000)	(196,000)
Amortization of Prior Service Cost (Credit)	1,000	1,000	2,000	2,000
Amortization of Net Actuarial Loss	27,000	31,000	80,000	93,000
Net Periodic Benefit Cost (Credit)	33,000	40,000	100,000	119,000
Pension Plans [Member] | Appalachian Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	2,175	1,759	6,525	5,277
Interest Cost	6,679	7,406	20,037	22,218
Expected Return on Plan Assets	(8,745)	(8,482)	(26,236)	(25,445)
Amortization of Prior Service Cost (Credit)	45	49	135	148
Amortization of Net Actuarial Loss	3,474	4,149	10,421	12,445
Net Periodic Benefit Cost (Credit)	3,628	4,881	10,882	14,643
Pension Plans [Member] | Indiana Michigan Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	3,217	2,517	9,651	7,551
Interest Cost	6,114	6,573	18,344	19,720
Expected Return on Plan Assets	(8,115)	(7,749)	(24,347)	(23,245)
Amortization of Prior Service Cost (Credit)	45	49	136	146
Amortization of Net Actuarial Loss	3,145	3,647	9,434	10,939
Net Periodic Benefit Cost (Credit)	4,406	5,037	13,218	15,111
Pension Plans [Member] | Ohio Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	1,671	1,285	5,015	3,855
Interest Cost	5,071	5,527	15,211	16,579
Expected Return on Plan Assets	(6,878)	(6,607)	(20,634)	(19,820)
Amortization of Prior Service Cost (Credit)	35	40	105	118
Amortization of Net Actuarial Loss	2,644	3,105	7,932	9,316
Net Periodic Benefit Cost (Credit)	2,543	3,350	7,629	10,048
Pension Plans [Member] | Public Service Co Of Oklahoma [Member]
Components of Net Periodic Benefit Cost
Service Cost	1,598	1,301	4,796	3,905
Interest Cost	2,731	3,015	8,194	9,043
Expected Return on Plan Assets	(3,786)	(3,651)	(11,358)	(10,953)
Amortization of Prior Service Cost (Credit)	63	74	189	222
Amortization of Net Actuarial Loss	1,418	1,689	4,252	5,065
Net Periodic Benefit Cost (Credit)	2,024	2,428	6,073	7,282
Pension Plans [Member] | Southwestern Electric Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	2,081	1,655	6,244	4,964
Interest Cost	2,932	3,163	8,796	9,488
Expected Return on Plan Assets	(4,008)	(3,857)	(12,024)	(11,571)
Amortization of Prior Service Cost (Credit)	78	87	232	262
Amortization of Net Actuarial Loss	1,506	1,762	4,520	5,285
Net Periodic Benefit Cost (Credit)	2,589	2,810	7,768	8,428
Other Postretirement Benefit Plans [Member]
Components of Net Periodic Benefit Cost
Service Cost	3,000	4,000	9,000	11,000
Interest Cost	15,000	16,000	43,000	50,000
Expected Return on Plan Assets	(28,000)	(28,000)	(83,000)	(84,000)
Amortization of Prior Service Cost (Credit)	(18,000)	(18,000)	(52,000)	(52,000)
Amortization of Net Actuarial Loss	5,000	6,000	14,000	17,000
Net Periodic Benefit Cost (Credit)	(23,000)	(20,000)	(69,000)	(58,000)
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	286	362	857	1,086
Interest Cost	2,584	3,197	7,753	9,591
Expected Return on Plan Assets	(4,529)	(4,634)	(13,587)	(13,900)
Amortization of Prior Service Cost (Credit)	(2,513)	(2,512)	(7,538)	(7,537)
Amortization of Net Actuarial Loss	900	1,145	2,699	3,436
Net Periodic Benefit Cost (Credit)	(3,272)	(2,442)	(9,816)	(7,324)
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	406	486	1,219	1,460
Interest Cost	1,592	1,909	4,776	5,728
Expected Return on Plan Assets	(3,304)	(3,363)	(9,912)	(10,090)
Amortization of Prior Service Cost (Credit)	(2,355)	(2,355)	(7,066)	(7,066)
Amortization of Net Actuarial Loss	506	592	1,519	1,776
Net Periodic Benefit Cost (Credit)	(3,155)	(2,731)	(9,464)	(8,192)
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	216	256	647	769
Interest Cost	1,615	1,900	4,845	5,701
Expected Return on Plan Assets	(3,376)	(3,379)	(10,130)	(10,139)
Amortization of Prior Service Cost (Credit)	(1,731)	(1,731)	(5,192)	(5,192)
Amortization of Net Actuarial Loss	517	595	1,552	1,785
Net Periodic Benefit Cost (Credit)	(2,759)	(2,359)	(8,278)	(7,076)
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member]
Components of Net Periodic Benefit Cost
Service Cost	170	209	509	629
Interest Cost	759	893	2,277	2,680
Expected Return on Plan Assets	(1,578)	(1,575)	(4,732)	(4,725)
Amortization of Prior Service Cost (Credit)	(1,072)	(1,072)	(3,217)	(3,217)
Amortization of Net Actuarial Loss	242	278	725	832
Net Periodic Benefit Cost (Credit)	(1,479)	(1,267)	(4,438)	(3,801)
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	211	253	632	759
Interest Cost	837	998	2,512	2,994
Expected Return on Plan Assets	(1,735)	(1,754)	(5,206)	(5,262)
Amortization of Prior Service Cost (Credit)	(1,289)	(1,289)	(3,867)	(3,867)
Amortization of Net Actuarial Loss	266	309	798	926
Net Periodic Benefit Cost (Credit)	$ (1,710)	$ (1,483)	$ (5,131)	$ (4,450)