CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net income	$ 279.9	$ 354.8	$ 284.3
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization expense	290.2	266.6	252.5
Recoveries and refunds of regulatory assets and liabilities	42.6	44.3	49.9
Net unrealized gains on energy contracts	(21.4)	(100.5)	(34.6)
Bad debt expense	51.6	34.4	26.2
Pension and other postretirement expense	19.0	62.1	62.3
Pension and other postretirement contributions	(108.8)	(77.0)	(287.9)
Deferred income taxes and investment tax credits	165.9	209.8	146.0
Gain on sale of UPPCO	(86.5)	0	0
Loss on sale of IES's retail energy business	24.3	0	0
Gain on sale or disposal of other assets	(15.2)	(1.8)	(2.7)
Equity income, net of dividends	(13.3)	(19.2)	(17.5)
Termination of tolling agreement with Fox Energy Company LLC	0	(50.0)	0
Other	43.5	34.9	25.3
Changes in working capital
Collateral on deposit	(46.5)	2.3	9.6
Accounts receivable and accrued unbilled revenues	11.2	(358.6)	(26.2)
Inventories	(124.4)	16.8	28.9
Other current assets	(11.6)	(50.4)	6.6
Accounts payable	12.7	142.9	21.8
Other current liabilities	88.2	43.5	29.3
Net cash provided by operating activities	601.4	554.9	573.8
Investing activities
Capital expenditures	(865.0)	(669.2)	(594.4)
Proceeds from the sale of UPPCO, net of cash divested	336.5	0	0
Proceeds from the sale of IES's retail energy business, net of cash divested	311.6	0	0
Proceeds from the sale or disposal of other assets	26.1	6.6	17.0
Capital contributions to equity method investments	(18.4)	(13.7)	(27.4)
Rabbi trust funding related to potential change in control	(115.5)	0	0
Acquisition of Fox Energy Company LLC	0	(391.6)	0
Acquisitions at IES	0	(15.7)	0
Grant received related to Crane Creek wind project	0	69.0	0
Other	(11.8)	(8.1)	2.2
Net cash used for investing activities	(336.5)	(1,022.7)	(602.6)
Financing activities
Short-term debt, net	(8.4)	(156.4)	179.1
Borrowing on term credit facility	0	200.0	0
Repayment of term credit facility	0	(200.0)	0
Issuance of long-term debt	200.0	1,174.0	428.0
Repayment of long-term debt	(175.0)	(363.5)	(305.2)
Proceeds from stock option exercises	85.8	38.7	55.8
Shares purchased for stock-based compensation	(142.9)	(2.0)	(89.9)
Payment of dividends
Preferred stock of subsidiary	(3.1)	(3.1)	(3.1)
Common stock	(216.3)	(202.6)	(211.9)
Other	(9.3)	(22.4)	(24.7)
Net cash (used for) provided by financing activities	(269.2)	462.7	28.1
Net change in cash and cash equivalents	(4.3)	(5.1)	(0.7)
Cash and cash equivalents at beginning of year	22.3	27.4	28.1
Cash and cash equivalents at end of year	18.0	22.3	27.4
Supplemental cash flow information
Cash paid for interest	146.8	116.1	109.7
Cash paid (received) for income taxes	$ 6.3	$ (4.8)	$ (47.6)