Receivables (Details of Accounts Receivable) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable [Line Items]
Customer	$ 93	$ 101
Unbilled utility revenues	91	82
Deferred proceeds	214	188
Other	53	59
Allowance for expected credit losses	(11)	(18)
Accounts receivable, less allowance for expected credit losses	440	412
IPL [Member]
Accounts Receivable [Line Items]
Customer	0	0
Unbilled utility revenues	0	0
Deferred proceeds	214	188
Other	28	23
Allowance for expected credit losses	(1)	(1)
Accounts receivable, less allowance for expected credit losses	241	210
WPL [Member]
Accounts Receivable [Line Items]
Customer	82	92
Unbilled utility revenues	91	82
Other	25	35
Allowance for expected credit losses	(10)	(17)
Accounts receivable, less allowance for expected credit losses	$ 188	$ 192