Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 309.5	$ 224.8
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	298.4	279.8
Deferred tax expense (benefit) and tax credits	(28.8)	19.9
Equity component of allowance for funds used during construction	(26.8)	(30.8)
Other	26.6	13.5
Other changes in assets and liabilities:
Accounts receivable	(197.9)	(199.7)
Accounts payable	8.3	(33.1)
Regulatory liabilities	(63.4)	(26.1)
Pension and other benefit obligations	(33.8)	(21.7)
Deferred income taxes	81.9	34.3
Other	(54.3)	16.0
Net cash flows from operating activities	319.7	276.9
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(584.0)	(652.5)
Other construction and acquisition expenditures	(24.3)	(54.1)
Cash receipts on sold receivables	209.9	125.5
Other	6.1	(25.9)
Net cash flows used for investing activities	(392.3)	(607.0)
Cash flows from financing activities:
Common stock dividends	(187.6)	(167.8)
Proceeds from issuance of common stock, net	234.8	60.6
Proceeds from issuance of long-term debt	1,050.0	650.0
Payments to retire long-term debt	(653.7)	(3.4)
Net change in commercial paper	(152.0)	(50.7)
Other	(27.2)	(9.9)
Net cash flows from financing activities	264.3	478.8
Net increase (decrease) in cash, cash equivalents and restricted cash	191.7	148.7
Cash, cash equivalents and restricted cash at beginning of period	17.7	25.5
Cash, cash equivalents and restricted cash at end of period	209.4	174.2
Supplemental cash flows information:
Interest	(138.1)	(132.7)
Income taxes, net	(5.0)	2.5
Significant non-cash investing and financing activities:
Accrued capital expenditures	208.3	187.4
Beneficial interest obtained in exchange for securitized accounts receivable	194.1	214.6
IPL [Member]
Cash flows from operating activities:
Net income	147.5	103.4
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	174.6	159.7
Deferred tax expense (benefit) and tax credits	(20.9)	(11.7)
Other	(5.8)	(14.9)
Other changes in assets and liabilities:
Accounts receivable	(218.7)	(209.3)
Accounts payable	26.1	(17.0)
Deferred income taxes	25.6	25.3
Other	(51.2)	53.5
Net cash flows from operating activities	77.2	89.0
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(309.6)	(449.5)
Cash receipts on sold receivables	209.9	125.5
Other	(25.5)	(30.5)
Net cash flows used for investing activities	(125.2)	(354.5)
Cash flows from financing activities:
Common stock dividends	(118.1)	(83.9)
Capital contributions from parent	175.0	100.0
Proceeds from issuance of long-term debt	400.0	300.0
Payments to retire long-term debt	(200.0)	0.0
Net change in commercial paper	0.0	(50.4)
Other	(14.7)	(6.2)
Net cash flows from financing activities	242.2	259.5
Net increase (decrease) in cash, cash equivalents and restricted cash	194.2	(6.0)
Cash, cash equivalents and restricted cash at beginning of period	9.3	12.4
Cash, cash equivalents and restricted cash at end of period	203.5	6.4
Supplemental cash flows information:
Interest	(71.6)	(58.3)
Income taxes, net	7.3	12.1
Significant non-cash investing and financing activities:
Accrued capital expenditures	93.8	117.4
Beneficial interest obtained in exchange for securitized accounts receivable	194.1	214.6
WPL [Member]
Cash flows from operating activities:
Net income	147.2	107.7
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	121.1	117.7
Other	(18.9)	17.0
Other changes in assets and liabilities:
Accounts receivable	23.1	7.6
Regulatory liabilities	(63.3)	(18.4)
Deferred income taxes	53.2	11.2
Other	(6.1)	(34.6)
Net cash flows from operating activities	256.3	208.2
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(274.4)	(203.0)
Other	14.6	(15.0)
Net cash flows used for investing activities	(259.8)	(218.0)
Cash flows from financing activities:
Common stock dividends	(84.0)	(72.0)
Capital contributions from parent	25.0	0.0
Proceeds from issuance of long-term debt	350.0	350.0
Payments to retire long-term debt	(150.0)	0.0
Net change in commercial paper	(130.3)	(105.5)
Other	(8.4)	(7.4)
Net cash flows from financing activities	2.3	165.1
Net increase (decrease) in cash, cash equivalents and restricted cash	(1.2)	155.3
Cash, cash equivalents and restricted cash at beginning of period	4.4	9.2
Cash, cash equivalents and restricted cash at end of period	3.2	164.5
Supplemental cash flows information:
Interest	(49.7)	(51.7)
Income taxes, net	1.1	(6.5)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 113.7	$ 66.4