Condensed Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:
Net income	$ 330.8	$ 308.1
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	288.4	277.4
Other amortizations	41.9	29.1
Deferred taxes and investment tax credits	54.2	92.2
Equity income from unconsolidated investments, net	(34.2)	(32.7)
Distributions from equity method investments	27.2	26.6
Other	(21.3)	(14.1)
Other changes in assets and liabilities:
Accounts receivable	96.1	(2.8)
Regulatory assets	(154.3)	(14.4)
Regulatory liabilities	61.1	(74.9)
Deferred income taxes	109.5	75.4
Other	(35.5)	(26.8)
Net cash flows from operating activities	763.9	643.1
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(587.4)	(524.4)
Alliant Energy Corporate Services, Inc. and non-regulated businesses construction and acquisition expenditures	(45.1)	(35.9)
Proceeds from Franklin County wind project cash grant	0	62.4
Other	(7.9)	(15.3)
Net cash flows used for investing activities	(640.4)	(513.2)
Cash flows from (used for) financing activities:
Common stock dividends	(169.3)	(156.2)
Preferred dividends paid by subsidiaries	(7.7)	(8.9)
Payments to redeem cumulative preferred stock	0	(211.0)
Proceeds from issuance of cumulative preferred stock	0	200.0
Payments to retire long-term debt	(47.7)	(0.8)
Net change in commercial paper	74.4	34.8
Other	28.0	8.7
Net cash flows from (used for) financing activities	(122.3)	(133.4)
Net increase (decrease) in cash and cash equivalents	1.2	(3.5)
Cash and cash equivalents at beginning of period	9.8	21.2
Cash and cash equivalents at end of period	11.0	17.7
Supplemental cash flows information:
Interest, net of capitalized interest	131.8	128.5
Income taxes, net of refunds	(5.3)	(9.7)
Significant non-cash investing and financing activities:
Accrued capital expenditures	141.1	100.5
IPL [Member]
Cash flows from operating activities:
Net income	172.0	168.8
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	146.9	142.8
Other	(12.8)	1.2
Other changes in assets and liabilities:
Accounts receivable	66.1	(43.0)
Regulatory assets	(126.1)	(9.8)
Regulatory liabilities	14.8	(68.3)
Deferred income taxes	112.5	71.0
Other	0.2	(3.0)
Net cash flows from operating activities	373.6	259.7
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(358.2)	(274.3)
Other	(18.3)	(15.5)
Net cash flows used for investing activities	(376.5)	(289.8)
Cash flows from (used for) financing activities:
Common stock dividends	(105.0)	(95.7)
Preferred dividends paid by subsidiaries	(7.7)	(8.3)
Capital contributions from parent	90.0	90.0
Payments to redeem cumulative preferred stock	0	(150.0)
Proceeds from issuance of cumulative preferred stock	0	200.0
Payments to retire long-term debt	(38.4)	0
Net change in commercial paper	38.0	(11.3)
Other	26.2	7.2
Net cash flows from (used for) financing activities	3.1	31.9
Net increase (decrease) in cash and cash equivalents	0.2	1.8
Cash and cash equivalents at beginning of period	4.4	4.5
Cash and cash equivalents at end of period	4.6	6.3
Supplemental cash flows information:
Interest, net of capitalized interest	64.2	60.9
Income taxes, net of refunds	(21.0)	10.7
Significant non-cash investing and financing activities:
Accrued capital expenditures	96.7	57.4
WPL [Member]
Cash flows from operating activities:
Net income	151.0	139.3
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	135.0	129.0
Other amortizations	36.1	21.9
Deferred taxes and investment tax credits	58.4	71.6
Equity income from unconsolidated investments, net	(34.2)	(32.7)
Distributions from equity method investments	27.2	26.6
Other	(7.3)	(5.4)
Other changes in assets and liabilities:
Accounts receivable	27.8	28.0
Regulatory assets	(28.2)	(4.6)
Derivative assets	(32.8)	3.4
Regulatory liabilities	46.3	(6.6)
Other	(13.5)	(14.3)
Net cash flows from operating activities	365.8	356.2
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(229.2)	(250.1)
Other	(4.6)	(2.3)
Net cash flows used for investing activities	(233.8)	(252.4)
Cash flows from (used for) financing activities:
Common stock dividends	(89.1)	(87.2)
Payments to redeem cumulative preferred stock	0	(61.0)
Net change in commercial paper	(37.0)	56.8
Other	(4.1)	(6.5)
Net cash flows from (used for) financing activities	(130.2)	(97.9)
Net increase (decrease) in cash and cash equivalents	1.8	5.9
Cash and cash equivalents at beginning of period	0.5	0.7
Cash and cash equivalents at end of period	2.3	6.6
Supplemental cash flows information:
Interest, net of capitalized interest	65.6	65.9
Income taxes, net of refunds	8.7	(0.6)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 39.9	$ 39.2