Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 376.2	$ 335.7	$ 321.9
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	370.9	332.9	323.8
Other amortizations	40.2	55.0	56.3
Deferred tax expense (benefit) and investment tax credits	108.3	143.3	10.2
Equity (income) loss from unconsolidated investments, net	(43.7)	(41.3)	(39.3)
Distributions from equity method investments	35.4	34.2	32.3
Equity component of allowance for funds used during construction	(20.3)	(14.1)	(7.6)
Non-cash valuation charges and other	(3.7)	0.7	20.3
Other changes in assets and liabilities:
Accounts receivable	(49.2)	61.3	(54.3)
Sales of accounts receivable	(101.0)	(10.0)	75.0
Regulatory assets	140.5	(178.1)	(413.1)
Regulatory liabilities	(90.8)	16.4	168.3
Deferred income taxes	101.9	69.7	147.3
Pension and other benefit obligations	(157.4)	51.3	8.9
Other	23.7	(15.9)	52.7
Net cash flows from operating activities	731.0	841.1	702.7
Cash flows used for investing activities:
Utility business - Riverside Energy Center	0	(403.5)	0
Utility business - other	(731.6)	(622.0)	(608.1)
Alliant Energy Corporate Services, Inc. and non-regulated businesses	(66.7)	(132.6)	(65.3)
Proceeds from Franklin County wind project cash grant	62.4	0	0
Collections of advances for customer energy efficiency projects	16.6	22.9	31.0
Other	(35.4)	(20.3)	(9.7)
Net cash flows used for investing activities	(754.7)	(1,155.5)	(652.1)
Cash flows from (used for) financing activities:
Common stock dividends	(208.3)	(199.3)	(188.1)
Preferred dividends paid by subsidiaries	(11.4)	(15.9)	(16.8)
Payments to redeem cumulative preferred stock	(211.0)	0	(40.0)
Proceeds from issuance of cumulative preferred stock of IPL	200.0	0	0
Proceeds from issuance of long-term debt	250.0	385.0	0.4
Net change in commercial paper	11.9	164.7	55.4
Other	(18.9)	(10.3)	(9.4)
Net cash flows from (used for) financing activities	12.3	324.2	(198.5)
Net increase (decrease) in cash and cash equivalents	(11.4)	9.8	(147.9)
Cash and cash equivalents at beginning of period	21.2	11.4	159.3
Cash and cash equivalents at end of period	9.8	21.2	11.4
Supplemental cash flows information:
Interest, net of capitalized interest	171.7	155.2	157.6
Income taxes, net of refunds	(9.6)	(20.3)	(10.8)
Significant non-cash investing and financing activities:
Accrued capital expenditures	103.8	105.3	49.7
IPL [Member]
Cash flows from operating activities:
Net income	189.9	150.2	139.3
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	191.1	188.9	179.1
Deferred tax expense (benefit) and investment tax credits	4.2	19.3	(58.6)
Equity component of allowance for funds used during construction	(13.8)	(5.2)	(3.5)
Non-cash valuation charges and other	(0.7)	10.6	23.5
Other changes in assets and liabilities:
Accounts receivable	(55.9)	(0.7)	22.4
Sales of accounts receivable	(101.0)	(10.0)	75.0
Regulatory assets	71.4	(129.0)	(328.8)
Regulatory liabilities	(82.3)	(12.1)	156.3
Deferred income taxes	92.4	64.6	145.5
Pension and other benefit obligations	(74.3)	21.0	(8.3)
Other	11.6	(6.6)	25.0
Net cash flows from operating activities	232.6	291.0	366.9
Cash flows used for investing activities:
Utility business - other	(400.2)	(307.5)	(293.7)
Proceeds from sale of wind project assets to affiliate	0	0	115.3
Other	(23.1)	(23.7)	(22.2)
Net cash flows used for investing activities	(423.3)	(331.2)	(200.6)
Cash flows from (used for) financing activities:
Common stock dividends	(128.1)	(122.9)	(73.4)
Preferred dividends paid by subsidiaries	(10.8)	(12.6)	(13.5)
Capital contributions from parent	120.0	110.0	54.0
Repayment of capital to parent	0	0	(100.7)
Payments to redeem cumulative preferred stock	(150.0)	0	(40.0)
Proceeds from issuance of cumulative preferred stock of IPL	200.0	0	0
Proceeds from issuance of long-term debt	250.0	0	0
Net change in commercial paper	(76.3)	69.2	7.1
Other	(14.2)	(1.1)	(3.4)
Net cash flows from (used for) financing activities	190.6	42.6	(169.9)
Net increase (decrease) in cash and cash equivalents	(0.1)	2.4	(3.6)
Cash and cash equivalents at beginning of period	4.5	2.1	5.7
Cash and cash equivalents at end of period	4.4	4.5	2.1
Supplemental cash flows information:
Interest, net of capitalized interest	80.7	78.3	78.0
Income taxes, net of refunds	(0.1)	3.3	25.3
Significant non-cash investing and financing activities:
Accrued capital expenditures	58.1	53.4	23.9
WPL [Member]
Cash flows from operating activities:
Net income	177.5	165.7	163.5
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	172.2	140.9	140.1
Other amortizations	29.5	43.7	42.4
Deferred tax expense (benefit) and investment tax credits	86.5	88.6	93.7
Equity (income) loss from unconsolidated investments, net	(43.7)	(42.1)	(38.7)
Distributions from equity method investments	35.4	34.2	32.3
Equity component of allowance for funds used during construction	(6.5)	(8.9)	(4.1)
Non-cash valuation charges and other	(0.2)	(2.9)	10.8
Other changes in assets and liabilities:
Income tax refunds receivable	(0.3)	(2.9)	39.9
Regulatory assets	69.1	(49.1)	(84.3)
Regulatory liabilities	(8.5)	28.5	12.0
Accrued taxes	(26.9)	19.2	(2.1)
Pension and other benefit obligations	(71.3)	31.7	8.8
Other	10.5	(19.2)	14.5
Net cash flows from operating activities	423.3	427.4	428.8
Cash flows used for investing activities:
Utility business - Riverside Energy Center	0	(403.5)	0
Utility business - other	(331.4)	(314.5)	(314.4)
Collections of advances for customer energy efficiency projects	15.8	20.9	26.8
Other	(20.3)	(13.1)	(17.8)
Net cash flows used for investing activities	(335.9)	(710.2)	(305.4)
Cash flows from (used for) financing activities:
Common stock dividends	(116.3)	(112.0)	(112.1)
Preferred dividends paid by subsidiaries	(0.6)	(3.3)	(3.3)
Capital contributions from parent	0	90.0	25.0
Repayment of capital to parent	0	0	0
Payments to redeem cumulative preferred stock	(61.0)	0	0
Proceeds from issuance of long-term debt	0	250.0	0
Net change in commercial paper	97.1	60.9	(21.7)
Other	(6.8)	(4.8)	(8.7)
Net cash flows from (used for) financing activities	(87.6)	280.8	(120.8)
Net increase (decrease) in cash and cash equivalents	(0.2)	(2.0)	2.6
Cash and cash equivalents at beginning of period	0.7	2.7	0.1
Cash and cash equivalents at end of period	0.5	0.7	2.7
Supplemental cash flows information:
Interest, net of capitalized interest	85.0	79.5	79.9
Income taxes, net of refunds	22.9	(3.3)	(51.3)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 37.7	$ 39.5	$ 19.7