Common Equity (Changes in Shareowners' Equity) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance			$ 5,205
Beginning balance	$ 5,748	$ 4,900	5,405	$ 4,786
Net income attributable to common shareowners	246	226	550	446
Net income	249	229	558	454
Common stock dividends	(94)	(85)	(281)	(253)
Equity forward settlements and Shareowner Direct Plan issuances	6	125	241	185
Equity-based compensation plans and other	3	3	5	6
Adoption of new accounting standard, net of tax			(9)
Other comprehensive loss, net of tax			(2)	(1)
Ending balance	5,709		5,709
Ending balance	$ 5,909	$ 5,169	$ 5,909	$ 5,169
Common stock dividends (in dollars per share)	$ 0.38	$ 0.355	$ 1.14	$ 1.065
Common Stock [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	$ 2	$ 2	$ 2	$ 2
Ending balance	2	2	2	2
Additional Paid-in Capital [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,683	2,109	2,446	2,046
Equity forward settlements and Shareowner Direct Plan issuances	6	125	241	185
Equity-based compensation plans and other	4	3	6	6
Ending balance	2,693	2,237	2,693	2,237
Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	2,874	2,598	2,766	2,546
Net income attributable to common shareowners	246	226	550	446
Common stock dividends	(94)	(85)	(281)	(253)
Ending balance	3,026	2,739	3,026	2,739
Accumulated Other Comprehensive Income (Loss) [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(1)	1	1	2
Other comprehensive loss, net of tax			(2)	(1)
Ending balance	(1)	1	(1)	1
Shares in Deferred Compensation Trust [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	(10)	(10)	(10)	(10)
Equity-based compensation plans and other	(1)		(1)
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			3,272
Beginning balance	3,671	3,345	3,472	3,231
Net income attributable to common shareowners	148	141	290	239
Net income	151	144	298	247
Common stock dividends	(59)	(42)	(177)	(126)
Capital contributions from parent	170		345	100
Ending balance	3,730		3,730
Ending balance	3,930	3,444	3,930	3,444
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	2,523	2,323	2,348	2,223
Capital contributions from parent	170		345	100
Ending balance	2,693	2,323	2,693	2,323
IPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	915	789	891	775
Net income attributable to common shareowners	148	141	290	239
Common stock dividends	(59)	(42)	(177)	(126)
Ending balance	1,004	888	1,004	888
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			2,364
Beginning balance	2,452	2,185	2,364	2,150
Net income	73	76	220	183
Common stock dividends	(43)	(36)	(127)	(108)
Capital contributions from parent		100	25	100
Ending balance	2,482		2,482
Ending balance	2,482	2,325	2,482	2,325
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	1,459	1,309	1,434	1,309
Capital contributions from parent		100	25	100
Ending balance	1,459	1,409	1,459	1,409
WPL [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Beginning balance	927	810	864	775
Net income	73	76	220	183
Common stock dividends	(43)	(36)	(127)	(108)
Ending balance	$ 957	$ 850	957	$ 850
Credit Losses ASU [Member] | Retained Earnings [Member]
Changes in Shareowners' Equity Roll Forward [Line Items]
Adoption of new accounting standard, net of tax			$ (9)