Disaggregation of Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 3,416	$ 3,648	$ 3,534
IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,947	2,089	2,042
WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,395	1,476	1,453
Electric [Member]
Disaggregation of Revenue [Line Items]
Revenues	2,920	3,064	3,000
Electric [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,695	1,781	1,731
Electric [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,225	1,283	1,269
Electric [Member] | Retail - Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	1,093	1,092	1,063
Electric [Member] | Retail - Residential [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	602	601	590
Electric [Member] | Retail - Residential [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	491	491	473
Electric [Member] | Retail - Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues	718	770	736
Electric [Member] | Retail - Commercial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	474	510	487
Electric [Member] | Retail - Commercial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	244	260	249
Electric [Member] | Retail - Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	841	889	889
Electric [Member] | Retail - Industrial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	488	504	501
Electric [Member] | Retail - Industrial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	353	385	388
Electric [Member] | Wholesale [Member]
Disaggregation of Revenue [Line Items]
Revenues	168	177	188
Electric [Member] | Wholesale [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	57	64	71
Electric [Member] | Wholesale [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	111	113	117
Electric [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	100	136	124
Electric [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	74	102	82
Electric [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	26	34	42
Gas [Member]
Disaggregation of Revenue [Line Items]
Revenues	373	455	447
Gas [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	208	264	266
Gas [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	165	191	181
Gas [Member] | Retail - Residential [Member]
Disaggregation of Revenue [Line Items]
Revenues	214	259	254
Gas [Member] | Retail - Residential [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	116	149	152
Gas [Member] | Retail - Residential [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	98	110	102
Gas [Member] | Retail - Commercial [Member]
Disaggregation of Revenue [Line Items]
Revenues	107	133	133
Gas [Member] | Retail - Commercial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	59	75	76
Gas [Member] | Retail - Commercial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	48	58	57
Gas [Member] | Retail - Industrial [Member]
Disaggregation of Revenue [Line Items]
Revenues	12	16	15
Gas [Member] | Retail - Industrial [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	8	12	10
Gas [Member] | Retail - Industrial [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	4	4	5
Gas [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	40	47	45
Gas [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	25	28	28
Gas [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	15	19	17
Other Utility [Member]
Disaggregation of Revenue [Line Items]
Revenues	49	46	48
Other Utility [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	44	44	45
Other Utility [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	5	2	3
Other Utility [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	13	9	13
Other Utility [Member] | Other [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	8	7	10
Other Utility [Member] | Other [Member] | WPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	5	2	3
Other Utility [Member] | Steam [Member]
Disaggregation of Revenue [Line Items]
Revenues	36	37	35
Other Utility [Member] | Steam [Member] | IPL [Member]
Disaggregation of Revenue [Line Items]
Revenues	36	37	35
Non-Utility and Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	74	83	39
Non-Utility and Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 74	$ 83	$ 39