Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 817	$ 763	$ 1,718	$ 1,679
Operating income (loss)	176	168	374	356
Net income attributable to common shareowners	144	134	315	304
Net income	146	136	320	309
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	455	432	944	951
Operating income (loss)	111	88	214	185
Net income attributable to common shareowners	86	60	165	142
Net income	88	62	170	147
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	341	312	736	687
Operating income (loss)	55	72	145	166
Net income	38	58	122	147
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	717	675	1,418	1,405
Operating income (loss)	164	152	311	298
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	402	388	788	813
Operating income (loss)	107	82	179	149
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	315	287	630	592
Operating income (loss)	57	70	132	149
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	69	59	239	211
Operating income (loss)	3	7	47	49
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	43	34	134	117
Operating income (loss)	3	5	33	33
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	26	25	105	94
Operating income (loss)	0	2	14	16
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	10	10	23	22
Operating income (loss)	(1)	1	1	4
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	10	10	22	21
Operating income (loss)	1	1	2	3
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	1	1
Operating income (loss)	(2)	0	(1)	1
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	796	744	1,680	1,638
Operating income (loss)	166	160	359	351
Net income attributable to common shareowners	124	118	287	289
Non-Utility [Member] | ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	21	19	38	41
Operating income (loss)	10	8	15	5
Net income attributable to common shareowners	$ 20	$ 16	$ 28	$ 15