Segments Of Business (Schedule Of Segments Of Business) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 901	$ 916
Operating income (loss)	198	188
Net income (loss) attributable to common shareowners	171	170
Net income	174	173
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	489	519
Operating income (loss)	103	97
Net income (loss) attributable to common shareowners	79	83
Net income	82	86
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	395	375
Operating income (loss)	90	94
Net income	84	90
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	701	730
Operating income (loss)	147	146
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	386	425
Operating income (loss)	72	67
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	315	305
Operating income (loss)	75	79
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	170	152
Operating income (loss)	44	41
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	91	83
Operating income (loss)	30	27
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	79	69
Operating income (loss)	14	14
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	13	12
Operating income (loss)	2	4
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	12	11
Operating income (loss)	1	3
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1	1
Operating income (loss)	1	1
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	884	894
Operating income (loss)	193	191
Net income (loss) attributable to common shareowners	163	173
Non-Utility [Member] | ATC Holdings, Non-Utility, Parent and Other [Member]
Segment Reporting Information [Line Items]
Revenues	17	22
Operating income (loss)	5	(3)
Net income (loss) attributable to common shareowners	$ 8	$ (3)