Debt (Other Short-Term Borrowings) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 793	$ 577
Average amount outstanding (based on daily outstanding balances)	$ 574	$ 443
Weighted average interest rates	4.80%	0.30%
WPL [Member]
Debt [Line Items]
Maximum amount outstanding (based on daily outstanding balances)	$ 349	$ 252
Average amount outstanding (based on daily outstanding balances)	$ 304	$ 205
Weighted average interest rates	4.80%	0.30%