Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income	$ 185.5	$ 169.3
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	204.6	200.6
Deferred tax expense and investment tax credits	46.1	43.0
Other	(28.8)	3.5
Other changes in assets and liabilities:
Accounts receivable	(59.5)	33.7
Sales of accounts receivable	133.0	78.0
Gas stored underground	21.7	44.0
Regulatory assets	34.7	(22.7)
Regulatory liabilities	(29.2)	(40.0)
Deferred income taxes	46.2	48.0
Other	(44.3)	(40.1)
Net cash flows from operating activities	510.0	517.3
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(491.0)	(436.2)
Alliant Energy Corporate Services, Inc. and non-regulated businesses construction and acquisition expenditures	(28.9)	(32.2)
Other	19.1	(1.9)
Net cash flows used for investing activities	(500.8)	(470.3)
Cash flows from (used for) financing activities:
Common stock dividends	(133.2)	(122.9)
Proceeds from issuance of common stock, net	13.8	139.5
Payments to retire long-term debt	(1.8)	(151.4)
Net change in commercial paper	127.8	90.8
Other	(15.1)	(5.1)
Net cash flows from (used for) financing activities	(8.5)	(49.1)
Net increase (decrease) in cash and cash equivalents	0.7	(2.1)
Cash and cash equivalents at beginning of period	5.8	56.9
Cash and cash equivalents at end of period	6.5	54.8
Supplemental cash flows information:
Interest, net of capitalized interest	(95.8)	(93.5)
Income taxes, net	(4.3)	0.1
Significant non-cash investing and financing activities:
Accrued capital expenditures	122.1	162.1
IPL [Member]
Cash flows from operating activities:
Net income	82.6	69.1
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	105.1	103.9
Other	3.4	25.4
Other changes in assets and liabilities:
Accounts receivable	(32.7)	16.9
Sales of accounts receivable	133.0	78.0
Regulatory liabilities	(30.2)	(38.9)
Accrued taxes	(14.5)	13.2
Deferred income taxes	44.0	44.7
Other	(18.9)	(17.8)
Net cash flows from operating activities	271.8	294.5
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(298.4)	(281.3)
Other	6.9	(3.9)
Net cash flows used for investing activities	(291.5)	(285.2)
Cash flows from (used for) financing activities:
Common stock dividends	(76.1)	(69.9)
Capital contributions from parent	40.0	100.0
Payments to retire long-term debt	0.0	(150.0)
Net change in commercial paper	67.0	111.2
Other	(13.3)	(3.9)
Net cash flows from (used for) financing activities	17.6	(12.6)
Net increase (decrease) in cash and cash equivalents	(2.1)	(3.3)
Cash and cash equivalents at beginning of period	4.5	5.3
Cash and cash equivalents at end of period	2.4	2.0
Supplemental cash flows information:
Interest, net of capitalized interest	(49.8)	(48.3)
Income taxes, net	(12.9)	18.6
Significant non-cash investing and financing activities:
Accrued capital expenditures	52.1	118.8
WPL [Member]
Cash flows from operating activities:
Net income	90.7	84.8
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	94.8	91.8
Deferred tax expense and investment tax credits	42.0	19.9
Other	(15.7)	(5.4)
Other changes in assets and liabilities:
Accounts receivable	(5.2)	18.6
Regulatory assets	37.5	(2.7)
Derivative liabilities	(13.9)	8.2
Other	21.2	15.0
Net cash flows from operating activities	251.4	230.2
Cash flows used for investing activities:
Utility business construction and acquisition expenditures	(192.6)	(154.9)
Other	(13.0)	(7.1)
Net cash flows used for investing activities	(205.6)	(162.0)
Cash flows from (used for) financing activities:
Common stock dividends	(67.5)	(63.5)
Net change in commercial paper	25.9	0.0
Other	(1.5)	(2.6)
Net cash flows from (used for) financing activities	(43.1)	(66.1)
Net increase (decrease) in cash and cash equivalents	2.7	2.1
Cash and cash equivalents at beginning of period	0.4	46.7
Cash and cash equivalents at end of period	3.1	48.8
Supplemental cash flows information:
Interest, net of capitalized interest	(45.7)	(46.5)
Income taxes, net	3.0	(3.7)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$ 62.7	$ 39.5