Fair Value Measurements (Fair Value Of Net Derivative Assets (Liabilities)) (Details) - Commodity Contracts [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 10	$ 29	$ 16	$ 29
Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3	9
Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	7	20
IPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	7	18	15	26
IPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3	8
IPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	4	10
WPL [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	3	11	$ 1	$ 3
WPL [Member] | Excluding Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	0	1
WPL [Member] | Financial Transmission Rights [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, net derivative assets	$ 3	$ 10