Commitments And Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Cumulative Effect, Period of Adoption, Adjustment [Member]
Long-term Purchase Commitment [Line Items]
New accounting standard, cumulative effect adjustment to retained earnings, pre-tax		$ 12
Whiting Petroleum Affiliate [Member]
Long-term Purchase Commitment [Line Items]
Partnership share, percent	6.00%
Obligations, maximum	$ 68
Credit loss liability	5
Credit loss expense	7
Capital Purchase Commitment [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	8
WPL [Member] | Capital Purchase Commitment [Member]
Long-term Purchase Commitment [Line Items]
Minimum future commitments	7
Indemnification Agreement [Member]
Long-term Purchase Commitment [Line Items]
Obligations, maximum	74
Indemnification Agreement [Member] | Purchased Power [Member]
Long-term Purchase Commitment [Line Items]
Obligations, maximum	17
FERC [Member]
Long-term Purchase Commitment [Line Items]
Base return on equity, percentage		9.88%	10.02%
FERC [Member] | IPL [Member]
Long-term Purchase Commitment [Line Items]
Refunds related to MISO base return on equity complaints	15
FERC [Member] | WPL [Member]
Long-term Purchase Commitment [Line Items]
Refunds related to MISO base return on equity complaints	$ 5