Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			$ 5,688
Beginning balance	$ 5,966	$ 5,702	5,888	$ 5,405
Net income attributable to common shareowners	144	134	315	304
Net income	146	136	320	309
Common stock dividends	(101)	(94)	(203)	(187)
Equity forward settlements and Shareowner Direct Plan issuances	7	7	15	235
Equity-based compensation plans and other	3	2	4	2
Adoption of new accounting standard, net of tax	(3,106)		(3,106)		$ (2,994)
Other comprehensive loss, net of tax		(3)		(2)
Ending balance	5,819		5,819
Ending balance	$ 6,019	$ 5,748	$ 6,019	$ 5,748
Common stock dividends (in dollars per share)	$ 0.4025	$ 0.38	$ 0.805	$ 0.76
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 3	$ 2	$ 2	$ 2
Equity forward settlements and Shareowner Direct Plan issuances			1
Ending balance	3	2	3	2
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,712	2,674	2,704	2,446
Equity forward settlements and Shareowner Direct Plan issuances	7	7	14	235
Equity-based compensation plans and other	3	2	4	2
Ending balance	2,722	2,683	2,722	2,683
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	3,063	2,834	2,994	2,766
Net income attributable to common shareowners	144	134	315	304
Common stock dividends	(101)	(94)	(203)	(187)
Ending balance	3,106	2,874	3,106	2,874
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(1)	2	(1)	1
Other comprehensive loss, net of tax		(3)		(2)
Ending balance	(1)	(1)	(1)	(1)
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(11)	(10)	(11)	(10)
Ending balance	(11)	(10)	(11)	(10)
Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	200	200	200	200
Ending balance	200	200	200	200
IPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			3,764
Beginning balance	3,942	3,595	3,964	3,472
Net income attributable to common shareowners	86	60	165	142
Net income	88	62	170	147
Common stock dividends	(99)	(59)	(200)	(118)
Adoption of new accounting standard, net of tax	(944)		(944)		(979)
Capital contributions from parent	50	75	50	175
Ending balance	3,779		3,779
Ending balance	3,979	3,671	3,979	3,671
IPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	33	33	33	33
Ending balance	33	33	33	33
IPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,752	2,448	2,752	2,348
Capital contributions from parent	50	75	50	175
Ending balance	2,802	2,523	2,802	2,523
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	957	914	979	891
Net income attributable to common shareowners	86	60	165	142
Common stock dividends	(99)	(59)	(200)	(118)
Ending balance	944	915	944	915
IPL [Member] | Cumulative Preferred Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	200	200	200	200
Ending balance	200	200	200	200
WPL [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			2,478
Beginning balance	2,645	2,436	2,478	2,364
Net income	38	58	122	147
Common stock dividends	(43)	(42)	(85)	(84)
Adoption of new accounting standard, net of tax	(990)		(990)		$ (953)
Capital contributions from parent	85		210	25
Ending balance	2,725		2,725
Ending balance	2,725	2,452	2,725	2,452
WPL [Member] | Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	66	66	66	66
Ending balance	66	66	66	66
WPL [Member] | Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	1,584	1,459	1,459	1,434
Capital contributions from parent	85		210	25
Ending balance	1,669	1,459	1,669	1,459
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	995	911	953	864
Net income	38	58	122	147
Common stock dividends	(43)	(42)	(85)	(84)
Ending balance	$ 990	$ 927	$ 990	$ 927
Credit Losses ASU [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Adoption of new accounting standard, net of tax						$ (9)