Segments Of Business (Schedule Of Segment Of Business) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 3,416	$ 3,648	$ 3,534
Depreciation and amortization	615	567	507
Operating income (loss)	740	778	694
Interest expense	275	273	247
Equity income from unconsolidated investments, net	(61)	(53)	(55)
Income tax expense (benefit)	(57)	69	48
Net income attributable to common shareowners	614	557	512
Total assets	17,710	16,701	15,426
Investments in equity method subsidiaries	476	458	421
Construction and acquisition expenditures	1,366	1,640	1,634
IPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,947	2,089	2,042
Operating income (loss)	410	403	351
Interest expense	139	127	119
Income tax expense (benefit)	(47)	24	(3)
Net income attributable to common shareowners	324	284	264
Total assets	9,849	9,277
WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,395	1,476	1,453
Operating income (loss)	306	347	313
Interest expense	104	102	98
Income tax expense (benefit)	(19)	49	36
Total assets	6,912	6,507
Electric [Member]
Segment Reporting Information [Line Items]
Revenues	2,920	3,064	3,000
Depreciation and amortization	556	513	457
Operating income (loss)	643	679	610
Equity income from unconsolidated investments, net	(2)	(1)	(1)
Total assets	14,358	13,659	12,486
Investments in equity method subsidiaries	11	9	8
Construction and acquisition expenditures	1,109	1,439	1,422
Electric [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,695	1,781	1,731
Depreciation and amortization	321	295	255
Operating income (loss)	358	360	318
Total assets	8,518	8,075	7,220
Construction and acquisition expenditures	626	964	891
Electric [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,225	1,283	1,269
Depreciation and amortization	235	218	202
Operating income (loss)	285	319	292
Total assets	5,840	5,584	5,266
Construction and acquisition expenditures	483	475	531
Gas [Member]
Segment Reporting Information [Line Items]
Revenues	373	455	447
Depreciation and amortization	49	47	42
Operating income (loss)	74	70	53
Equity income from unconsolidated investments, net	0	0	0
Total assets	1,413	1,269	1,184
Investments in equity method subsidiaries	0	0	0
Construction and acquisition expenditures	182	100	147
Gas [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	208	264	266
Depreciation and amortization	30	29	25
Operating income (loss)	50	39	28
Total assets	766	734	687
Construction and acquisition expenditures	59	56	100
Gas [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	165	191	181
Depreciation and amortization	19	18	17
Operating income (loss)	24	31	25
Total assets	647	535	497
Construction and acquisition expenditures	123	44	47
Other Utility [Member]
Segment Reporting Information [Line Items]
Revenues	49	46	48
Depreciation and amortization	5	3	3
Operating income (loss)	(1)	1	1
Equity income from unconsolidated investments, net	0	0	0
Total assets	990	856	893
Investments in equity method subsidiaries	0	0	0
Construction and acquisition expenditures	2	0	0
Other Utility [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	44	44	45
Depreciation and amortization	5	3	3
Operating income (loss)	2	4	5
Total assets	565	468	504
Construction and acquisition expenditures	2	0	0
Other Utility [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	5	2	3
Depreciation and amortization	0	0	0
Operating income (loss)	(3)	(3)	(4)
Total assets	425	388	389
Construction and acquisition expenditures	0	0	0
Utility Business [Member]
Segment Reporting Information [Line Items]
Revenues	3,342	3,565	3,495
Depreciation and amortization	610	563	502
Operating income (loss)	716	750	664
Interest expense	243	229	217
Equity income from unconsolidated investments, net	(2)	(1)	(1)
Income tax expense (benefit)	(66)	73	33
Net income attributable to common shareowners	573	517	472
Total assets	16,761	15,784	14,563
Investments in equity method subsidiaries	11	9	8
Construction and acquisition expenditures	1,293	1,539	1,569
Utility Business [Member] | IPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,947	2,089	2,042
Depreciation and amortization	356	327	283
Operating income (loss)	410	403	351
Interest expense	139	127	119
Income tax expense (benefit)	(47)	24	(3)
Net income attributable to common shareowners	324	284	264
Total assets	9,849	9,277	8,411
Construction and acquisition expenditures	687	1,020	991
Utility Business [Member] | WPL [Member]
Segment Reporting Information [Line Items]
Revenues	1,395	1,476	1,453
Depreciation and amortization	254	236	219
Operating income (loss)	306	347	313
Interest expense	104	102	98
Income tax expense (benefit)	(19)	49	36
Net income attributable to common shareowners	249	233	208
Total assets	6,912	6,507	6,152
Construction and acquisition expenditures	606	519	578
Non-Utility [Member]
Segment Reporting Information [Line Items]
Revenues	74	83	39
Depreciation and amortization	5	4	5
Operating income (loss)	24	28	30
Interest expense	32	44	30
Equity income from unconsolidated investments, net	(59)	(52)	(54)
Income tax expense (benefit)	9	(4)	15
Net income attributable to common shareowners	41	40	40
Total assets	949	917	863
Investments in equity method subsidiaries	465	449	413
Construction and acquisition expenditures	$ 73	$ 101	$ 65