Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Revenues	$ 1,024	$ 920	$ 2,742	$ 2,599
Operating income (loss)	289	272	663	628
Net income attributable to common shareowners	256	246	571	550
Net income	259	249	579	558
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	599	553	1,543	1,504
Operating income (loss)	180	162	394	347
Net income attributable to common shareowners	157	148	322	290
Net income	160	151	330	298
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	403	351	1,139	1,038
Operating income (loss)	100	89	245	255
Net income	93	73	215	220
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	939	852	2,357	2,257
Operating income (loss)	290	251	601	549
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	555	519	1,343	1,332
Operating income (loss)	186	159	365	308
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	384	333	1,014	925
Operating income (loss)	104	92	236	241
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	50	42	289	253
Operating income (loss)	(5)	(1)	42	48
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	31	24	165	141
Operating income (loss)	(3)	1	30	34
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	19	18	124	112
Operating income (loss)	(2)	(2)	12	14
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	13	10	36	32
Operating income (loss)	(5)	1	(4)	5
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	13	10	35	31
Operating income (loss)	(3)	2	(1)	5
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	1	1
Operating income (loss)	(2)	(1)	(3)	0
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	1,002	904	2,682	2,542
Operating income (loss)	280	251	639	602
Net income attributable to common shareowners	250	221	537	510
Non-Utility [Member] | ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	22	16	60	57
Operating income (loss)	9	21	24	26
Net income attributable to common shareowners	$ 6	$ 25	$ 34	$ 40