CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating Activities
Net income	$ 188.3	$ 99.7
Adjustments to reconcile net income to net cash provided by operating activities
Discontinued operations, net of tax	(6.1)	(0.9)
Depreciation and amortization expense	60.9	62.1
Recoveries and refunds of regulatory assets and liabilities	16.5	9.5
Net unrealized (gains) losses on energy contracts	(65.2)	43.7
Bad debt expense	9.3	10.1
Pension and other postretirement expense	15.9	17.5
Pension and other postretirement contributions	(63.2)	(246.2)
Deferred income taxes and investment tax credits	68.3	29.7
Equity income, net of dividends	(4.4)	(3.8)
Termination of tolling agreement with Fox Energy Company LLC	(50.0)
Other	6.3	2.7
Changes in working capital
Collateral on deposit	15.4	(13.7)
Accounts receivable and accrued unbilled revenues	(182.8)	49.8
Inventories	137.9	133.0
Other current assets	45.4	54.6
Accounts payable	24.7	(77.7)
Temporary LIFO liquidation credit	83.2	36.7
Other current liabilities	19.2	18.0
Net cash provided by operating activities	319.6	224.8
Investing Activities
Capital expenditures	(147.0)	(123.0)
Proceeds from the sale or disposal of assets	1.1	1.4
Capital contributions to equity method investments	(1.7)	(10.4)
Acquisition of Fox Energy Company LLC	(391.6)
Grant received related to Crane Creek Wind Project	69.0
Other	(3.0)	(4.6)
Net cash used for investing activities	(473.2)	(136.6)
Financing Activities
Short-term debt, net	74.0	2.2
Borrowing on term credit facility	200.0
Repayment of long-term debt	(22.0)
Proceeds from stock option exercises	6.4	10.1
Shares purchased for stock-based compensation	(2.0)	(24.6)
Payment of dividends
Preferred stock of subsidiary	(0.8)	(0.8)
Common stock	(50.1)	(53.0)
Payments made on derivative contracts related to divestitures classified as financing activities	(3.8)	(9.0)
Other	(4.5)	0.2
Net cash provided by (used for) financing activities	197.2	(74.9)
Change in cash and cash equivalents - continuing operations	43.6	13.3
Change in cash and cash equivalents - discontinued operations
Net cash (used for) provided by operating activities	(0.6)	1.0
Net cash provided by (used for) investing activities	1.6	(0.1)
Net change in cash and cash equivalents	44.6	14.2
Cash and cash equivalents at beginning of period	27.4	28.1
Cash and cash equivalents at end of period	$ 72.0	$ 42.3