Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Pension Plans [Member]
Components of Net Periodic Benefit Cost
Service Cost	$ 24,000	$ 18,000	$ 47,000	$ 36,000
Interest Cost	52,000	56,000	103,000	111,000
Expected Return on Plan Assets	(68,000)	(65,000)	(137,000)	(131,000)
Amortization of Prior Service Cost (Credit)	0	0	1,000	1,000
Amortization of Net Actuarial Loss	26,000	31,000	53,000	62,000
Net Periodic Benefit Cost (Credit)	34,000	40,000	67,000	79,000
Pension Plans [Member] | Appalachian Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	2,175	1,759	4,350	3,518
Interest Cost	6,679	7,406	13,358	14,812
Expected Return on Plan Assets	(8,746)	(8,481)	(17,491)	(16,963)
Amortization of Prior Service Cost (Credit)	45	49	90	99
Amortization of Net Actuarial Loss	3,474	4,148	6,947	8,296
Net Periodic Benefit Cost (Credit)	3,627	4,881	7,254	9,762
Pension Plans [Member] | Indiana Michigan Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	3,217	2,517	6,434	5,034
Interest Cost	6,115	6,574	12,230	13,147
Expected Return on Plan Assets	(8,116)	(7,748)	(16,232)	(15,496)
Amortization of Prior Service Cost (Credit)	46	48	91	97
Amortization of Net Actuarial Loss	3,144	3,646	6,289	7,292
Net Periodic Benefit Cost (Credit)	4,406	5,037	8,812	10,074
Pension Plans [Member] | Ohio Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	1,672	1,285	3,344	2,570
Interest Cost	5,070	5,526	10,140	11,052
Expected Return on Plan Assets	(6,878)	(6,606)	(13,756)	(13,213)
Amortization of Prior Service Cost (Credit)	35	39	70	78
Amortization of Net Actuarial Loss	2,644	3,105	5,288	6,211
Net Periodic Benefit Cost (Credit)	2,543	3,349	5,086	6,698
Pension Plans [Member] | Public Service Co Of Oklahoma [Member]
Components of Net Periodic Benefit Cost
Service Cost	1,599	1,302	3,198	2,604
Interest Cost	2,732	3,014	5,463	6,028
Expected Return on Plan Assets	(3,786)	(3,651)	(7,572)	(7,302)
Amortization of Prior Service Cost (Credit)	63	74	126	148
Amortization of Net Actuarial Loss	1,417	1,688	2,834	3,376
Net Periodic Benefit Cost (Credit)	2,025	2,427	4,049	4,854
Pension Plans [Member] | Southwestern Electric Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	2,082	1,654	4,163	3,309
Interest Cost	2,932	3,162	5,864	6,325
Expected Return on Plan Assets	(4,008)	(3,857)	(8,016)	(7,714)
Amortization of Prior Service Cost (Credit)	77	88	154	175
Amortization of Net Actuarial Loss	1,507	1,762	3,014	3,523
Net Periodic Benefit Cost (Credit)	2,590	2,809	5,179	5,618
Other Postretirement Benefit Plans [Member]
Components of Net Periodic Benefit Cost
Service Cost	3,000	3,000	6,000	7,000
Interest Cost	14,000	17,000	28,000	34,000
Expected Return on Plan Assets	(27,000)	(28,000)	(55,000)	(56,000)
Amortization of Prior Service Cost (Credit)	(17,000)	(17,000)	(34,000)	(34,000)
Amortization of Net Actuarial Loss	4,000	6,000	9,000	11,000
Net Periodic Benefit Cost (Credit)	(23,000)	(19,000)	(46,000)	(38,000)
Other Postretirement Benefit Plans [Member] | Appalachian Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	285	362	571	724
Interest Cost	2,585	3,197	5,169	6,394
Expected Return on Plan Assets	(4,529)	(4,633)	(9,058)	(9,266)
Amortization of Prior Service Cost (Credit)	(2,512)	(2,512)	(5,025)	(5,025)
Amortization of Net Actuarial Loss	899	1,145	1,799	2,291
Net Periodic Benefit Cost (Credit)	(3,272)	(2,441)	(6,544)	(4,882)
Other Postretirement Benefit Plans [Member] | Indiana Michigan Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	407	487	813	974
Interest Cost	1,592	1,910	3,184	3,819
Expected Return on Plan Assets	(3,304)	(3,363)	(6,608)	(6,727)
Amortization of Prior Service Cost (Credit)	(2,356)	(2,356)	(4,711)	(4,711)
Amortization of Net Actuarial Loss	507	592	1,013	1,184
Net Periodic Benefit Cost (Credit)	(3,154)	(2,730)	(6,309)	(5,461)
Other Postretirement Benefit Plans [Member] | Ohio Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	215	257	431	513
Interest Cost	1,615	1,900	3,230	3,801
Expected Return on Plan Assets	(3,378)	(3,380)	(6,754)	(6,760)
Amortization of Prior Service Cost (Credit)	(1,730)	(1,730)	(3,461)	(3,461)
Amortization of Net Actuarial Loss	518	595	1,035	1,190
Net Periodic Benefit Cost (Credit)	(2,760)	(2,358)	(5,519)	(4,717)
Other Postretirement Benefit Plans [Member] | Public Service Co Of Oklahoma [Member]
Components of Net Periodic Benefit Cost
Service Cost	169	210	339	420
Interest Cost	759	894	1,518	1,787
Expected Return on Plan Assets	(1,577)	(1,575)	(3,154)	(3,150)
Amortization of Prior Service Cost (Credit)	(1,072)	(1,073)	(2,145)	(2,145)
Amortization of Net Actuarial Loss	241	277	483	554
Net Periodic Benefit Cost (Credit)	(1,480)	(1,267)	(2,959)	(2,534)
Other Postretirement Benefit Plans [Member] | Southwestern Electric Power Co [Member]
Components of Net Periodic Benefit Cost
Service Cost	210	253	421	506
Interest Cost	838	998	1,675	1,996
Expected Return on Plan Assets	(1,736)	(1,754)	(3,471)	(3,508)
Amortization of Prior Service Cost (Credit)	(1,289)	(1,289)	(2,578)	(2,578)
Amortization of Net Actuarial Loss	266	308	532	617
Net Periodic Benefit Cost (Credit)	$ (1,711)	$ (1,484)	$ (3,421)	$ (2,967)