CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Activities
Net income (loss)	$ 230.5	$ 223.7	$ (67.5)
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Discontinued operations, net of tax	0.4	(0.2)	(2.8)
Goodwill impairment loss			291.1
Impairment losses on property, plant, and equipment	4.6	43.2	0.7
Depreciation and amortization expense	250.1	265.8	230.6
Recoveries and refunds of regulatory assets and liabilities	56.1	28.7	40.8
Net unrealized (gains) losses on nonregulated energy contracts	48.5	(55.8)	104.2
Nonregulated lower of cost or market inventory adjustments	11.6	0.9	44.2
Bad debt expense	35.0	48.0	54.6
Pension and other postretirement expense	60.0	67.6	72.4
Pension and other postretirement contributions	(131.5)	(201.8)	(53.3)
Deferred income taxes and investment tax credits	175.3	234.1	58.3
(Gain) loss on sale of assets	(2.2)	11.4	24.1
Equity income, net of dividends	(14.8)	(14.5)	(16.1)
Other	32.5	33.3	37.7
Changes in working capital
Collateral on deposit	(17.3)	163.6	45.5
Accounts receivable and accrued unbilled revenues	94.1	97.6	864.8
Inventories	(28.0)	51.1	444.1
Other current assets	46.2	(85.5)	39.6
Accounts payable	(37.4)	(25.8)	(604.7)
Other current liabilities	(91.8)	(160.2)	(2.0)
Net cash provided by operating activities	721.9	725.2	1,606.3
Investing Activities
Capital expenditures	(311.4)	(258.8)	(444.2)
Proceeds from the sale or disposal of assets	7.6	66.0	44.6
Capital contributions to equity method investments	(37.6)	(6.9)	(34.1)
Acquisition of compressed natural gas fueling companies, net of cash acquired	(42.6)
Other	(10.8)		(7.0)
Net cash used for investing activities	(394.8)	(199.7)	(440.7)
Financing Activities
Short-term debt, net	303.3	(212.1)	(815.7)
Redemption of notes payable	(10.0)		(157.9)
Proceeds from sale of borrowed natural gas		21.9	162.0
Purchase of natural gas to repay natural gas loans		(6.5)	(445.2)
Issuance of long-term debt	50.0	250.0	230.0
Repayment of long-term debt	(565.8)	(117.2)	(157.8)
Payment of dividends
Preferred stock of subsidiary	(3.1)	(3.1)	(3.1)
Common stock	(206.4)	(186.1)	(206.9)
Issuance of common stock	4.9	33.2
Proceeds from derivative contracts related to divestitures classified as financing activities			33.9
Payments made on derivative contracts related to divestitures classified as financing activities	(31.9)	(157.8)
Other	(19.4)	(13.7)	(17.7)
Net cash used for financing activities	(478.4)	(391.4)	(1,378.4)
Change in cash and cash equivalents - continuing operations	(151.3)	134.1	(212.8)
Change in cash and cash equivalents - discontinued operations
Net cash provided by investing activities	0.4	0.4	3.2
Net change in cash and cash equivalents	(150.9)	134.5	(209.6)
Cash and cash equivalents at beginning of year	179.0	44.5	254.1
Cash and cash equivalents at end of year	$ 28.1	$ 179.0	$ 44.5