Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 920	$ 990	$ 2,599	$ 2,768
Operating income (loss)	272	290	628	617
Net income attributable to common shareowners	246	226	550	446
Net income	249	229	558	454
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	553	597	1,504	1,593
Operating income (loss)	162	174	347	322
Net income attributable to common shareowners	148	141	290	239
Net income	151	144	298	247
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	351	372	1,038	1,113
Operating income (loss)	89	108	255	273
Net income	73	76	220	183
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	852	916	2,257	2,350
Operating income (loss)	251	284	549	543
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	519	561	1,332	1,373
Operating income (loss)	159	175	308	291
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	333	355	925	977
Operating income (loss)	92	109	241	252
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	42	42	253	323
Operating income (loss)	(1)	(5)	48	47
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	24	25	141	188
Operating income (loss)	1	(4)	34	26
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	18	17	112	135
Operating income (loss)	(2)	(1)	14	21
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	10	11	32	33
Operating income (loss)	1	3	5	5
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	10	11	31	32
Operating income (loss)	2	3	5	5
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	1	1
Operating income (loss)	(1)	0	0	0
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	904	969	2,542	2,706
Operating income (loss)	251	282	602	595
Net income attributable to common shareowners	221	217	510	422
Non-Utility [Member] | ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	16	21	57	62
Operating income (loss)	21	8	26	22
Net income attributable to common shareowners	$ 25	$ 9	$ 40	$ 24