CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities
Net income	$ 354.8	$ 284.3	$ 230.5
Adjustments to reconcile net income to net cash provided by operating activities
Discontinued operations, net of tax	(4.8)	9.7	(0.5)
Depreciation and amortization expense	266.6	250.7	247.7
Recoveries and refunds of regulatory assets and liabilities	44.3	49.9	56.1
Net unrealized (gains) losses on energy contracts	(102.2)	(40.3)	45.2
Bad debt expense	34.4	26.2	35.0
Pension and other postretirement expense	62.1	62.1	59.9
Pension and other postretirement contributions	(77.0)	(287.5)	(131.5)
Deferred income taxes and investment tax credits	198.5	148.2	174.1
Equity income, net of dividends	(19.2)	(17.5)	(14.8)
Termination of tolling agreement with Fox Energy Company LLC	(50.0)	0	0
Other	41.0	20.1	45.9
Changes in working capital
Collateral on deposit	2.3	9.6	(17.3)
Accounts receivable and accrued unbilled revenues	(358.8)	(26.2)	93.4
Inventories	16.8	28.5	(37.1)
Other current assets	(42.0)	6.1	55.3
Accounts payable	143.1	22.0	(37.3)
Other current liabilities	45.1	23.1	(86.8)
Net cash provided by operating activities	555.0	569.0	717.8
Investing activities
Capital expenditures	(669.2)	(594.3)	(310.1)
Capital contributions to equity method investments	(13.7)	(27.4)	(37.6)
Acquisition of Fox Energy Company LLC	(391.6)	0	0
Acquisitions at Integrys Energy Services	(15.7)	0	0
Grant received related to Crane Creek wind project	69.0	0	0
Acquisition of compressed natural gas fueling companies, net of cash acquired	0	1.3	(42.6)
Other	(3.1)	15.4	(3.2)
Net cash used for investing activities	(1,024.3)	(605.0)	(393.5)
Financing activities
Short-term debt, net	(156.4)	179.1	303.3
Repayment of notes payable	0	0	(10.0)
Borrowing on term credit facility	200.0	0	0
Repayment of term credit facility	(200.0)	0	0
Issuance of long-term debt	1,174.0	428.0	50.0
Repayment of long-term debt	(363.5)	(278.2)	(565.8)
Proceeds from stock option exercises	38.7	55.8	10.3
Shares purchased for stock-based compensation	(2.0)	(89.9)	(17.0)
Payment of dividends
Preferred stock of subsidiary	(3.1)	(3.1)	(3.1)
Common stock	(202.6)	(211.9)	(206.4)
Payments made on derivative contracts related to divestitures classified as financing activities	(5.8)	(23.7)	(31.9)
Other	(16.6)	(1.0)	(7.5)
Net cash provided by (used for) financing activities	462.7	55.1	(478.1)
Change in cash and cash equivalents - continuing operations	(6.6)	19.1	(153.8)
Change in cash and cash equivalents - discontinued operations
Net cash (used for) provided by operating activities	(0.1)	4.8	4.1
Net cash provided by (used for) investing activities	1.6	2.4	(0.9)
Net cash used for financing activities	0	(27.0)	(0.3)
Net change in cash and cash equivalents	(5.1)	(0.7)	(150.9)
Cash and cash equivalents at beginning of year	27.4	28.1	179.0
Cash and cash equivalents at end of year	22.3	27.4	28.1
Supplemental cash flow information
Cash paid for interest	116.1	109.7	130.7
Cash received for income taxes	$ (4.8)	$ (47.6)	$ (80.0)