Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from (used for) operating activities:
Net income	$ 624	$ 567	$ 522
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	615	567	507
Deferred tax expense (benefit) and tax credits	(66)	56	67
Equity component of allowance for funds used during construction	(39)	(66)	(51)
Other	37	20	8
Other changes in assets and liabilities:
Accounts receivable	(468)	(472)	(475)
Regulatory assets	(130)	(16)	(16)
Regulatory liabilities	(113)	(40)	1
Deferred income taxes	171	54	56
DAEC PPA amendment buyout payment	(110)	0	0
Other	(20)	(10)	(91)
Net cash flows from (used for) operating activities	501	660	528
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(1,293)	(1,539)	(1,569)
Other construction and acquisition expenditures	(73)	(101)	(65)
Cash receipts on sold receivables	458	413	605
Other	(43)	(60)	(38)
Net cash flows used for investing activities	(951)	(1,287)	(1,067)
Cash flows from financing activities:
Common stock dividends	(377)	(337)	(312)
Proceeds from issuance of common stock, net	247	390	197
Proceeds from issuance of long-term debt	1,250	950	1,500
Payments to retire long-term debt	(657)	(256)	(856)
Net change in commercial paper and other short-term borrowings	52	(104)	26
Other	(27)	(24)	(24)
Net cash flows from (used for) financing activities	488	619	531
Net increase (decrease) in cash, cash equivalents and restricted cash	38	(8)	(8)
Cash, cash equivalents and restricted cash at beginning of period	18	26	34
Cash, cash equivalents and restricted cash at end of period	56	18	26
Supplemental cash flows information:
Interest	(274)	(268)	(247)
Income taxes, net	5	21	(5)
Significant non-cash investing and financing activities:
Accrued capital expenditures	131	196	299
Beneficial interest obtained in exchange for securitized accounts receivable	188	188	119
IPL [Member]
Cash flows from (used for) operating activities:
Net income	334	294	274
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	356	327	283
Deferred tax expense (benefit) and tax credits	(52)	15	2
Equity component of allowance for funds used during construction	(17)	(35)	(29)
Other	12	1	4
Other changes in assets and liabilities:
Accounts receivable	(466)	(467)	(494)
Regulatory assets	(93)	(11)	(20)
Accounts payable	6	(21)	(25)
Regulatory liabilities	(20)	2	1
Deferred income taxes	79	35	44
DAEC PPA amendment buyout payment	(110)	0	0
Other	(35)	33	(45)
Net cash flows from (used for) operating activities	(6)	173	(5)
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(687)	(1,020)	(991)
Cash receipts on sold receivables	458	413	605
Other	(72)	(60)	(44)
Net cash flows used for investing activities	(301)	(667)	(430)
Cash flows from financing activities:
Common stock dividends	(236)	(168)	(168)
Capital contributions from parent	404	125	425
Proceeds from issuance of long-term debt	400	600	500
Payments to retire long-term debt	(200)	0	(350)
Net change in commercial paper and other short-term borrowings	0	(50)	50
Other	(20)	(16)	(17)
Net cash flows from (used for) financing activities	348	491	440
Net increase (decrease) in cash, cash equivalents and restricted cash	41	(3)	5
Cash, cash equivalents and restricted cash at beginning of period	9	12	7
Cash, cash equivalents and restricted cash at end of period	50	9	12
Supplemental cash flows information:
Interest	(141)	(122)	(120)
Income taxes, net	(18)	7	(24)
Significant non-cash investing and financing activities:
Accrued capital expenditures	73	112	187
Beneficial interest obtained in exchange for securitized accounts receivable	188	188	119
WPL [Member]
Cash flows from (used for) operating activities:
Net income	249	233	208
Adjustments to reconcile net income to net cash flows from (used for) operating activities:
Depreciation and amortization	254	236	219
Deferred tax expense (benefit) and tax credits	(15)	24	50
Other	2	(12)	(17)
Other changes in assets and liabilities:
Regulatory liabilities	(93)	(42)	1
Deferred income taxes	90	20	9
Other	(21)	(36)	(13)
Net cash flows from (used for) operating activities	466	423	457
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(606)	(519)	(578)
Other	(7)	(38)	(30)
Net cash flows used for investing activities	(613)	(557)	(608)
Cash flows from financing activities:
Common stock dividends	(160)	(144)	(140)
Capital contributions from parent	25	125	200
Proceeds from issuance of long-term debt	350	350	0
Payments to retire long-term debt	(150)	(250)	0
Net change in commercial paper and other short-term borrowings	89	63	81
Other	(8)	(15)	(5)
Net cash flows from (used for) financing activities	146	129	136
Net increase (decrease) in cash, cash equivalents and restricted cash	(1)	(5)	(15)
Cash, cash equivalents and restricted cash at beginning of period	4	9	24
Cash, cash equivalents and restricted cash at end of period	3	4	9
Supplemental cash flows information:
Interest	(102)	(103)	(98)
Income taxes, net	13	(29)	14
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 55	$ 82	$ 102