Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income	$ 453.4	$ 434.5
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	423.6	376.4
Deferred tax expense and tax credits	53.2	62.5
Equity component of allowance for funds used during construction	(46.3)	(35.5)
Other	17.1	2.1
Other changes in assets and liabilities:
Accounts receivable	(359.2)	(325.2)
Accounts payable	(27.9)	(47.3)
Deferred income taxes	45.4	32.7
Other	(50.1)	(58.0)
Net cash flows from operating activities	509.2	442.2
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(1,003.9)	(1,080.2)
Other construction and acquisition expenditures	(71.4)	(47.8)
Cash receipts on sold receivables	255.9	337.2
Other	(41.7)	(24.9)
Net cash flows used for investing activities	(861.1)	(815.7)
Cash flows from (used for) financing activities:
Common stock dividends	(252.5)	(233.3)
Proceeds from issuance of common stock, net	185.4	191.3
Proceeds from issuance of long-term debt	950.0	1,500.0
Payments to retire long-term debt	(253.5)	(603.1)
Net change in commercial paper and other short-term borrowings	(91.6)	(278.4)
Other	(11.7)	10.9
Net cash flows from (used for) financing activities	526.1	587.4
Net increase (decrease) in cash, cash equivalents and restricted cash	174.2	213.9
Cash, cash equivalents and restricted cash at beginning of period	25.5	33.9
Cash, cash equivalents and restricted cash at end of period	199.7	247.8
Supplemental cash flows information:
Interest	(194.7)	(171.6)
Income taxes, net	0.8	(5.0)
Significant non-cash investing and financing activities:
Accrued capital expenditures	254.2	236.2
Beneficial interest obtained in exchange for securitized accounts receivable	237.0	243.7
IPL [Member]
Cash flows from operating activities:
Net income	247.1	232.6
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	243.4	209.2
Equity component of allowance for funds used during construction	(24.6)	(19.3)
Other	(13.2)	0.7
Other changes in assets and liabilities:
Accounts receivable	(365.0)	(353.2)
Accounts payable	(14.0)	(34.5)
Deferred income taxes	31.5	22.9
Other	33.3	(19.5)
Net cash flows from operating activities	138.5	38.9
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(696.3)	(635.2)
Cash receipts on sold receivables	255.9	337.2
Other	(43.7)	(30.9)
Net cash flows used for investing activities	(484.1)	(328.9)
Cash flows from (used for) financing activities:
Common stock dividends	(126.0)	(125.9)
Capital contributions from parent	100.0	230.0
Proceeds from issuance of long-term debt	600.0	500.0
Payments to retire long-term debt	0.0	(100.0)
Net change in commercial paper and other short-term borrowings	(50.4)	0.0
Other	(5.1)	15.0
Net cash flows from (used for) financing activities	518.5	519.1
Net increase (decrease) in cash, cash equivalents and restricted cash	172.9	229.1
Cash, cash equivalents and restricted cash at beginning of period	12.4	7.2
Cash, cash equivalents and restricted cash at end of period	185.3	236.3
Supplemental cash flows information:
Interest	(93.9)	(89.1)
Income taxes, net	8.2	(2.4)
Significant non-cash investing and financing activities:
Accrued capital expenditures	180.2	142.4
Beneficial interest obtained in exchange for securitized accounts receivable	237.0	243.7
WPL [Member]
Cash flows from operating activities:
Net income	183.2	170.1
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	176.6	164.2
Deferred tax expense and tax credits	54.6	50.3
Other	(7.8)	(12.0)
Other changes in assets and liabilities:
Accounts receivable	3.8	29.7
Regulatory liabilities	(28.6)	7.2
Other	(22.2)	(64.0)
Net cash flows from operating activities	359.6	345.5
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(307.6)	(445.0)
Other	(27.3)	(23.7)
Net cash flows used for investing activities	(334.9)	(468.7)
Cash flows from (used for) financing activities:
Common stock dividends	(107.9)	(105.0)
Capital contributions from parent	100.0	200.0
Proceeds from issuance of long-term debt	350.0	0.0
Payments to retire long-term debt	(250.0)	0.0
Net change in commercial paper and other short-term borrowings	(105.5)	13.4
Other	(10.9)	(1.7)
Net cash flows from (used for) financing activities	(24.3)	106.7
Net increase (decrease) in cash, cash equivalents and restricted cash	0.4	(16.5)
Cash, cash equivalents and restricted cash at beginning of period	9.2	24.2
Cash, cash equivalents and restricted cash at end of period	9.6	7.7
Supplemental cash flows information:
Interest	(73.9)	(68.5)
Income taxes, net	(7.0)	(11.2)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 70.3	$ 86.2