Condensed Consolidated Statements Of Cash Flows (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 174.9	$ 147.9
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	191.3	185.3
Other amortizations	28.9	19.3
Deferred taxes and investment tax credits	37.3	40.8
Equity income from unconsolidated investments, net	(22.7)	(21.6)
Distributions from equity method investments	18.3	17.4
Other	(12.8)	(9.6)
Other changes in assets and liabilities:
Accounts receivable	47.6	(16.4)
Sales of accounts receivable	(19.0)	5.0
Derivative assets	(92.3)	(34.3)
Regulatory assets	(71.6)	(19.7)
Accounts payable	35.8	53.3
Regulatory liabilities	45.2	(15.1)
Deferred income taxes	51.5	43.4
Other	35.8	27.6
Net cash flows from operating activities	448.2	423.3
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(332.6)	(341.5)
Alliant Energy Corporate Services, Inc. and non-regulated businesses construction and acquisition expenditures	(31.9)	(27.5)
Proceeds from Franklin County wind project cash grant	0	62.4
Other	(4.5)	(15.6)
Net cash flows used for investing activities	(369.0)	(322.2)
Cash flows from (used for) financing activities:
Common stock dividends	(112.9)	(104.2)
Preferred dividends paid by subsidiaries	(5.1)	(6.3)
Payments to redeem cumulative preferred stock	0	(211.0)
Proceeds from issuance of cumulative preferred stock	0	200.0
Net change in commercial paper	28.5	10.6
Other	16.7	0.1
Net cash flows from (used for) financing activities	(72.8)	(110.8)
Net increase (decrease) in cash and cash equivalents	6.4	(9.7)
Cash and cash equivalents at beginning of period	9.8	21.2
Cash and cash equivalents at end of period	16.2	11.5
Supplemental cash flows information:
Interest, net of capitalized interest	90.5	86.7
Income taxes, net of refunds	(3.8)	(9.7)
Significant non-cash investing and financing activities:
Accrued capital expenditures	124.9	94.1
IPL [Member]
Cash flows from operating activities:
Net income	66.9	56.2
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	97.6	95.2
Other	(4.0)	(8.7)
Other changes in assets and liabilities:
Accounts receivable	48.3	(33.7)
Sales of accounts receivable	(19.0)	5.0
Production fuel	22.6	4.1
Derivative assets	(51.9)	(27.6)
Regulatory assets	(48.5)	(13.2)
Accounts payable	23.4	51.3
Regulatory liabilities	(2.7)	(27.1)
Deferred income taxes	54.7	43.1
Other	18.7	29.1
Net cash flows from operating activities	206.1	173.7
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(184.9)	(180.0)
Other	(11.5)	(9.8)
Net cash flows used for investing activities	(196.4)	(189.8)
Cash flows from (used for) financing activities:
Common stock dividends	(70.0)	(63.5)
Preferred dividends paid by subsidiaries	(5.1)	(5.7)
Capital contributions from parent	60.0	60.0
Payments to redeem cumulative preferred stock	0	(150.0)
Proceeds from issuance of cumulative preferred stock	0	200.0
Net change in commercial paper	0	(21.3)
Other	6.4	(2.8)
Net cash flows from (used for) financing activities	(8.7)	16.7
Net increase (decrease) in cash and cash equivalents	1.0	0.6
Cash and cash equivalents at beginning of period	4.4	4.5
Cash and cash equivalents at end of period	5.4	5.1
Supplemental cash flows information:
Interest, net of capitalized interest	45.2	41.5
Income taxes, net of refunds	(9.0)	2.2
Significant non-cash investing and financing activities:
Accrued capital expenditures	76.1	56.2
WPL [Member]
Cash flows from operating activities:
Net income	89.4	78.0
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	89.4	86.3
Other amortizations	24.9	14.4
Deferred taxes and investment tax credits	37.1	39.1
Equity income from unconsolidated investments, net	(22.8)	(21.6)
Distributions from equity method investments	18.3	17.4
Other	(3.6)	(3.6)
Other changes in assets and liabilities:
Accounts receivable	14.1	19.7
Derivative assets	(40.4)	(6.7)
Regulatory assets	(23.1)	(6.5)
Regulatory liabilities	47.9	12.0
Other	4.3	(3.3)
Net cash flows from operating activities	235.5	225.2
Cash flows used for investing activities:
Utility construction and acquisition expenditures	(147.7)	(161.5)
Other	(3.4)	(2.8)
Net cash flows used for investing activities	(151.1)	(164.3)
Cash flows from (used for) financing activities:
Common stock dividends	(59.4)	(58.2)
Payments to redeem cumulative preferred stock	0	(61.0)
Net change in commercial paper	(25.7)	62.3
Other	6.6	(2.2)
Net cash flows from (used for) financing activities	(78.5)	(59.1)
Net increase (decrease) in cash and cash equivalents	5.9	1.8
Cash and cash equivalents at beginning of period	0.5	0.7
Cash and cash equivalents at end of period	6.4	2.5
Supplemental cash flows information:
Interest, net of capitalized interest	42.2	42.5
Income taxes, net of refunds	9.4	8.5
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 46.7	$ 36.8