Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income	$ 172.6	$ 127.7
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	146.3	136.9
Deferred tax expense and tax credits	(22.5)	21.7
Other	5.3	(10.1)
Other changes in assets and liabilities:
Accounts receivable	(119.0)	(121.6)
Gas stored underground	13.7	33.1
Accounts payable	(6.2)	(42.7)
Regulatory liabilities	(38.1)	14.1
Pension and other benefit obligations	(31.4)	(15.4)
Deferred income taxes	49.6	16.9
Other	(10.1)	20.5
Net cash flows from operating activities	160.2	181.1
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(277.9)	(374.0)
Other construction and acquisition expenditures	(10.6)	(32.1)
Cash receipts on sold receivables	122.5	53.4
Other	(13.6)	(12.1)
Net cash flows used for investing activities	(179.6)	(364.8)
Cash flows from (used for) financing activities:
Common stock dividends	(93.0)	(83.7)
Proceeds from issuance of common stock, net	228.4	54.6
Proceeds from issuance of long-term debt	300.0	0.0
Payments to retire long-term debt	(300.3)	(0.3)
Net change in commercial paper and other short-term borrowings	(66.9)	188.5
Other	(7.9)	16.9
Net cash flows from (used for) financing activities	60.3	176.0
Net increase (decrease) in cash, cash equivalents and restricted cash	40.9	(7.7)
Cash, cash equivalents and restricted cash at beginning of period	17.7	25.5
Cash, cash equivalents and restricted cash at end of period	58.6	17.8
Supplemental cash flows information:
Interest	(64.9)	(62.9)
Income taxes, net	(0.1)	6.8
Significant non-cash investing and financing activities:
Accrued capital expenditures	156.3	167.5
Beneficial interest obtained in exchange for securitized accounts receivable	188.0	178.3
IPL [Member]
Cash flows from operating activities:
Net income	85.2	55.9
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	85.9	77.1
Other	(15.3)	(10.1)
Other changes in assets and liabilities:
Accounts receivable	(125.5)	(112.6)
Gas stored underground	13.4	20.7
Other	(18.6)	45.7
Net cash flows from operating activities	25.1	76.7
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(165.0)	(261.3)
Cash receipts on sold receivables	122.5	53.4
Other	(10.4)	(13.9)
Net cash flows used for investing activities	(52.9)	(221.8)
Cash flows from (used for) financing activities:
Common stock dividends	(59.0)	(42.0)
Capital contributions from parent	100.0	100.0
Net change in commercial paper and other short-term borrowings	0.0	64.6
Other	2.5	17.0
Net cash flows from (used for) financing activities	43.5	139.6
Net increase (decrease) in cash, cash equivalents and restricted cash	15.7	(5.5)
Cash, cash equivalents and restricted cash at beginning of period	9.3	12.4
Cash, cash equivalents and restricted cash at end of period	25.0	6.9
Supplemental cash flows information:
Interest	(40.9)	(36.0)
Income taxes, net	(0.1)	6.8
Significant non-cash investing and financing activities:
Accrued capital expenditures	92.4	106.6
Beneficial interest obtained in exchange for securitized accounts receivable	188.0	178.3
WPL [Member]
Cash flows from operating activities:
Net income	89.6	65.7
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	59.1	58.6
Other	(15.5)	12.8
Other changes in assets and liabilities:
Accounts payable	(2.9)	(28.7)
Regulatory liabilities	(39.2)	(3.3)
Deferred income taxes	32.3	4.0
Other	24.8	13.1
Net cash flows from operating activities	148.2	122.2
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(112.9)	(112.7)
Other	(11.6)	(7.6)
Net cash flows used for investing activities	(124.5)	(120.3)
Cash flows from (used for) financing activities:
Common stock dividends	(42.1)	(36.0)
Capital contributions from parent	25.0	0.0
Net change in commercial paper and other short-term borrowings	13.8	32.9
Other	(2.1)	(3.3)
Net cash flows from (used for) financing activities	(5.4)	(6.4)
Net increase (decrease) in cash, cash equivalents and restricted cash	18.3	(4.5)
Cash, cash equivalents and restricted cash at beginning of period	4.4	9.2
Cash, cash equivalents and restricted cash at end of period	22.7	4.7
Supplemental cash flows information:
Interest	(21.4)	(22.5)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 62.0	$ 57.3